Trisha Dey

Adenine is a nine membered cyclic purine nucleobase, not a sugar.

Adenine is made up of two separate cyclic molecules fused to each other via an edge (a six-membered pyrimidine ring and a five-membered imidazole ring). Also unlike sugars or carbohydrates Nitrogen is a major component of adenine influencing its chemical properties.

So if asked “Is adenine sugar?” the answer would simply be no. Adenine is closely associated with sugars in the form of ribose and deoxyribose in DNA, RNA, AMP, ADP and ATP. But Adenine in itself is far from being a sugar itself.

Why is adenine sugar?

In biological terms or explanations, Adenine can never be called sugar or carbohydrate.

Carbohydrates or simple sugars are composed of 3 main components- Oxygen, Hydrogen and Oxygen. Whereas Nitrogen is a major component of nucleobases like Adenine.

Carbohydrates or sugars, in general, have a neutral chemical composition and nature. On the other hand, adenine is a nitrogenous base as is found to be an H⁺  or proton donor.

How is adenine sugar?

Adenine is not considered a sugar or sugar derivative chemically.

Adenine is a purine nitrogenous base molecule found in nucleic acids and some other biomolecules. In most of these structures, we find adenine attached to other sugars.

Carbon, Hydrogen and Oxygen atoms are the main components in sugar or carbohydrate structures, sometimes having substitutes side chains. They usually occur in cyclic structures and mainly five-membered or six-membered ringed monomers joined together.

Usually, they are chemically neutral unlike nitrogenous bases like Adenine. Adenine is more complex due to the presence of a six-membered pyrimidine ring fused to an imidazole ring that is made up of five atoms. The final structure is a nine membered complex molecule.

What sugar is in adenine?

Adenine is a purine base, not a sugar or carbohydrate.

Adenine is a nitrogenous purine(nine membered ring structure) base. It is a part of nucleic acids like DNA and RNA, but it’s not an acid in and of itself.

Adenine is closely associated with sugars like – deoxyribose and ribose. DNA and RNA nucleotides also contain adenine, along with the phosphates Adenosine Monophosphate (AMP), Adenosine Diphosphate (ADP), and Adenosine Triphosphate (ATP).

Another proof that adenine is not a sugar, is that we cannot salvage sugar or other carbohydrates to obtain adenine via the salvage pathway of nucleotide synthesis. Nucleotides can only be produced from the breakdown of amino acids.

Is adenine a deoxyribose sugar?

Biologically classified Adenine is a cyclic nitrogenous base.

Adenine is present in both DNA and RNA and can be attached to both ribose and deoxyribose. But Adenine in itself is a nine membered cyclic molecule.

A nucleotide containing adenine is one of the nitrogenous bases found in DNA. A DNA nucleotide is composed of three parts: a nitrogenous base (such as Adenine, Guanine, Thymine or Cytosine), a sugar molecule called deoxyribose and a phosphate group. Adenine, Guanine, Thymine, or Cytosine are examples of nitrogenous bases.

These nitrogenous bases are what allow the 2 antiparallel DNA strands to bond and form the double helix structure. Hence Adenine is not a deoxyribose sugar but attached to it in a DNA nucleotide.

What sugar is found in Flavin Adenine Dinucleotide (FAD)?

Flavin Adenine Dinucleotide or FAD structure technically possesses only one sugar molecule, a ribose.

One FAD molecule is made up of two parts- an adenine nucleotide or adenine monophosphate(AMP) joined with a Flavin mononucleotide-(FMN) or riboflavin-5’-phosphate, via their phosphate groups.

The AMP is made up of one Adenine, a ribose sugar and a phosphate group forming a typical mononucleotide molecule also seen in RNA. While riboflavin-5′-phosphate is a molecule derived from Vitamin B2 or Riboflavin under the effect of an enzyme called riboflavin kinase.

So the only sugar found in the structure of FAD is a ribose.

When adenine is attached to a ribose sugar?

Adenine can be found attached to ribose sugar in – RNA nucleotide, AMP, ADP and ATP.

Adenine is a key integrant of all nucleic acids, and it binds to Thymine and Uracil, in DNA and RNA respectively. Adenine is also one of the constituents of Adenosine Triphosphate, which serves as the cellular energy currency.

The nucleotide for RNA has 3 parts:

• A sugar which in the case of  RNA is ribose
• A nitrogenous base- Adenine, Uracil, Guanine or Cytosine and
• A phosphate group

So adenine can be found attached to ribose in the RNA nucleotides.Also in molecules like Adenosine Monophosphate (AMP), Adenosine Diphosphate (ADP) and Adenosine Triphosphate (ATP), we see that Adenine is attached to a ribose sugar and one, two or three phosphate groups respectively.

AMP is in itself an RNA nucleotide, while ADP and ATP are important energy suppliers in biological cells. They can act as catalyzers or enzymes and provide energy themselves or help process other reactions.

Hence in the above biomolecules, we can find Adenine attached to ribose sugars naturally.

Also Read:

• Do animal cells have vacuoles
• Protease enzyme example
• Protein synthesis structure
• Multiple fruit example
• Crustacean characteristics
• Do animal cells have a central vacuole
• Adenosine nucleoside nucleoside phosphoramidite
• Nectar flower example
• Are bacteria invertebrates
• Light dependent reaction example

Nucleotides are the unit monomers of nucleic acids.

In vivo i.e. inside a cell, there are exactly two methods for nucleotide synthesis- salvage and de novo. Salvage is to break down old nucleic acids whereas by the de novo method we synthesize new nucleotide molecules.

So how are nucleotides produced? The anabolic process of biochemically combining a phosphate group, a pentose sugar(ribose or deoxy-ribose) and a nitrogenous base is called de novo nucleotide synthesis. On the other hand, Nucleic acid destruction is a catabolic process, from which parts can be salvaged by the salvage pathway to produce new nucleotides as well.

How is a nucleotide formed in DNA?

Nucleotides are made up of trimeric monomers called nucleotides. Long chains of these nucleotides make up nucleic acid polymers like DNA and RNA.

 DNA nucleotide is made up of 3 main components- a pentose sugar(deoxyribose), a phosphate group and a nitrogenous base. A total of four different nitrogenous bases can be found in DNA including- Adenine, Guanine, Thymine and Cytosine.

All nucleotides are made up of three separate chemical subunits: a five-carbon sugar molecule, a nucleobase (together called a nucleoside), and one phosphate group. Depending on the sugar and nitrogenous base we can differ the nucleotide of the 2 different nucleic acids.

Where do nucleotides come from?

Nucleotides can be produced in vitro(outside a living organism) or in vivo(inside a living organism).

 Scientists often use groups like phosphoramidite in the laboratory to make nucleotides in vitro. Nucleotides can be produced from scratch(de novo mechanism) in the body(in vivo) or recycled through salvage mechanisms.

The salvage pathway is one in which a biological product is made from reaction intermediates produced while getting rid of a biomolecule. Nucleotide salvage, in which nucleotides (purine and pyrimidine) are produced from intermediates that are being catabolized or degraded.

Bases and nucleosides that are generated during the breakdown of RNA and DNA are recovered via nucleotide salvage processes. This is significant in some organs since some tissues cannot be synthesised from scratch. The nucleotides can then be made from the recovered goods. Drug research is focusing on salvage routes, one of which is known as antifolates.

Instead of recycling or partial breakdown of byproducts, the de novo pathway refers to the production of new complex molecular compounds from simple molecules such as sugars or amino acids. Nucleotides, for example, are not required in the diet since they may be made from tiny precursor molecules like formate and aspartate. Methionine is an essential amino acid as the body cannot synthesize it from scratch. Hence the only way of input is via our diet.

Nucleotide synthesis pathway:

As discussed above nucleotide synthesis mainly occurs by 2 methods:

• De novo pathway
• Salvage pathway

Here we will discuss the 2 processes in detail.

DE NOVO NUCLEOTIDE SYNTHESIS:

 De novo is a Latin word that translates to “from the beginning.” It may also mean “anew,” “from scratch,” or “from the outset.” The de novo pathway enzymes use 5-phosphoribosyl-1-pyrophosphate (PRPP) to produce new purine and pyrimidine nucleotides from “scratch bottom” by making use of simple biomolecules like amino acids and tetrahydrofolate.

 In comparison to the salvage process, this mechanism of nucleotide synthesis has a high energy need. Five of the 12 stages of de novo purine synthesis, for example, need ATP or GTP hydrolysis, although just one salvage cycle process does.

Both of these biosynthetic pathways have something in common-  the presence of some proteins characterized as “housekeeping enzymes”. However seeing that they are quite essential to cellular regulations, they are thought to be present in minute quantities in all living cells. While the de novo route enzymes are assumed to be found in plastids, salvage cycle enzymes might be found in several compartments.

Free nitrogenous bases like Adenine (A), Guanine (G), Cytosine (C), Thymine (T), and Uracil (U) are not used in the de novo nucleotide pathway. Throughout the process, the purine ring is constructed either one atom or a few atoms at a time and connected to ribose. The pyrimidine ring is formed by attaching orotate to ribose phosphate and then converting it to common pyrimidine nucleotides.

SALVAGE PATHWAY:

Bases and nucleosides are recovered from RNA and DNA degradation or external sources and converted back to nucleotides via nucleotide salvage processes. This is significant in some organs since some tissues cannot be synthesized from scratch. The nucleotides can then be made from the recovered goods. Drug research is focusing on salvage routes, one of which is known as antifolates.

A variety of nucleases break down nucleic acids into their constituent nucleotides. Nucleosides are further broken down by several nucleobases and phosphatases. The component bases are released in the third stage of hydrolysis by nucleosidases and nucleoside phosphorylases.

The steps for purine and pyrimidine synthesis are slightly different. Here we will discuss some of them:

• Pyrimidine salvage pathway

In the case of Uracil: Pyrimidine-nucleoside phosphorylase or simply uridine phosphorylase just substitutes free uracil on the anomeric-carbon-bonded phosphate of ribose 1-phosphate with uridine.

 Uridine kinase (also known as uridine–cytidine kinase) can then phosphorylate the nucleoside’s 5′-carbon to produce uridine monophosphate (UMP). UMP/CMP kinase converts UMP to uridine diphosphate, which nucleoside diphosphate kinase converts to uridine triphosphate.

In the case of Cytidine: Both nucleoside cytidine and deoxycytidine are usually salvaged by the enzyme cytidine deaminase, and converted to uridine and deoxyuridine respectively. Alternatively, they can be phosphorylated by uridine–cytidine kinase into cytidine monophosphate (CMP) or deoxycytidine monophosphate (DMP) by uridine–cytidine kinase (d-CMP).

 The enzyme UM Pkinase or CMP kinase converts dCMP to cytidine diphosphate or deoxycytidine diphosphate. This cytidine diphosphate is converted to cytidine triphosphate or deoxycytidine triphosphate by nucleoside diphosphate kinase enzyme.

In the case of thymine: Thymidine is recycled to produce dTMP by an enzyme called Thymidine kinase. Thymidine phosphorylase or pyrimidine-nucleoside phosphorylase, adds a 2-deoxy-alpha-D-ribose 1-phosphate group to thymine, creating the deoxynucleoside thymidine, which occurs when thymine binds to the 5’ C of deoxyribose. Thymidine kinase then phosphorylates this compound’s 5′-carbon to produce thymidine monophosphate (TMP). TMP may be phosphorylated by thymidylate kinase into thymidine diphosphate, which can then be phosphorylated by nucleoside diphosphate kinase into thymidine triphosphate.

• Purine salvage pathway

In the case of guanine: A guanosine kinase recycles guanosine to produce GMP. A guanosine phosphorylase may convert it to guanine, which could then be turned to GMP by a guanine phosphoribosyltransferase.

In the case of Adenine: An adenosine kinase might use adenosine directly in the production of AMP, or an adenosine nucleosidase and an adenine phosphoribosyltransferase could use adenine.

 In the biosynthesis of IMP, adenine might be recycled through a series of processes mediated by four enzymes:

1. an adenosine phosphorylase yielding adenosine,
2. an adenosine deaminase producing inosine,
3. an inosine phosphorylase that yields hypoxanthine    and
4. an IMP synthesized by hypoxanthine phosphoribosyltransferase.

Also Read:

• Does glycolysis occur in the mitochondria
• Kingdom fungi examples
• Is dna polymerase an enzyme
• Is nucleus a cell organelle
• Cell without cytoplasm
• Genetic diversity in meiosis
• What is the function of ribosomes
• Light independent reaction in photosynthesis
• How is atp formed during photosynthesis 2
• Is cytoplasm an organelle

Splicing is the process of converting hetero-nuclear RNA to messenger RNA in the eukaryotic central dogma.

RNA splicing is a mechanism in which genetic information is changed while in RNA-form during eukaryotic gene expression. The process is called post-transcriptional processing i.e it is a part of RNA transcription from the gene.

An explanation of the transmission of genetic information inside a biological system is the core tenet of molecular biology. Although this is not its original meaning, it is sometimes phrased as “DNA produces RNA, and RNA makes protein.” This is the core mechanism o the Central Dogma.

Simplistically it means conversion of DNA(gene) to RNA to protein via transcription and translation and occurs in both prokaryotes and eukaryotes. The RNA splicing steps are discussed below.

RNA splicing definition:

In terms of molecular biology, RNA splicing is one of the processes involved in converting an mRNA precursor to a mature mRNA. This is done by removing the introns or the non-coding genes in the pre-mRNA or hnRNA and joining only the coding genes or exons to form the mRNA chain.

For genes encoded in the nucleus as in eukaryotes, splicing occurs immediately after transcription and is called a post-transcriptional process.

RNA splicing mechanism:

The process of splicing occurs in several steps. The RNA splicing steps are:

• Step1: Formation and activation of different spliceosome complexes
• Step2: Finding the starting and ending points of the introns and removing them
• Step3: Joining the exons together.

Formation of the spliceosome and the spliceosome location the introns and cutting them off occur simultaneously in the same step, followed by the joining of the exons.

FORMATION OF THE SPLICEOSOME:

Splicing in hnRNA is initiated by the spliceosome, a large RNA-protein complex made up of five small nuclear ribonucleoproteins (snRNPs). The spliceosome is assembled and activated during the transcription of the hnRNA. SnRNPs’ RNA components interact with the intron and have a role in catalysis. There are two kinds of spliceosomes (major and minor) that contain various snRNPs.

In this process, 2 types of spliceosomes are produced- the major spliceosome and the minor spliceosome. These two types of spliceosomes have distinctly different functions.

RECOGNITION OF THE INTRON SITES:

Major spliceosome:

The Major spliceosome splices introns with G(Guanine)U(Uracil) sequence at the 5′ splice site and A(Adenine)G(Guanine) sequence at the 3′ splice site. It is active in the nucleus and is made up of the 6 snRNPs-U1, U2, U4, U5, and U6. Spliceosome formation also requires several proteins, including U2 small nuclear RNA auxiliary factor 1 (U2AF35), U2AF2 (U2AF65), and SF1 (Splicing Factor 1). During the process of RNA splicing, several complexes with diverse functions are produced by the spliceosome including:

Complex E:

• U1 snRNP goes and binds to the GU sequence in an intron’s 5′-splice site
• Splicing factor1(SF1) binds to the same intron’s branchpoint sequence;
• U2AF1 binds to the splice site present on the 3’ end of the intron;
•  U2AF2 goes to bind itself to the polypyrimidine tract;

Complex A (pre-spliceosome complex)

• The U2 snRNP attaches to the branch point sequence and displaces Splicing Factor 1, causing ATP to be hydrolyzed.

Complex B

• Three snRNPs-U5, U4 and U6 bind together to form a trimeric complex, where the U5 snRNP binds to exons at the 5′ site while U6 binds to U2.

Complex B*:

• The U1 snRNP complex is released. After the positions of the U5 shift from the exon to the intron, the U6 goes and binds to the 5′ splice site that was previously occupied by the U5.

Complex C (catalytic spliceosome):

• The U4 snRNP is released At the same time the U6/U2 catalyses transesterification(exchanging the organic group R” group of an ester molecule with the organic group R’ group of an alcohol molecule).
• The 5′ end of the intron goes around to ligate to the Adenine on itself, forming a lariat; the U5 binds exon at the 3′ splice site, and the 5′ site is cleaved, forming the lariat; and the U5 binds exon at the 3′ splice site, causing the lariat to form.

Canonical splicing, also known as the lariat route, is the most common kind of splicing that occurs in nature. It accounts for more than 99% of all splicing that occurs in all RNA varieties.

When the sequences flanking on the sides of the intron do not obey the GU-AG (GuanineUracil- GuanineAdenine) rule, it is referred to as noncanonical splicing.

Minor spliceosome:

The function of the minor spliceosome is quite similar to that of the major spliceosome, but it splices out uncommon introns with distinct splice site sequences. While the U5 snRNP is similar in both the minor and major spliceosomes, the minor spliceosome possesses distinct but functionally analogous snRNPs for U1, U2, U4, and U6, known as U11, U12, U4atac, and U6atac respectively.

JOINING OF THE EXONS:

This involves Complex C* which is a post-spliceosomal complex. The last step of splicing constitutes the cleaving of the  3′ site and litigation of the exons utilising ATP hydrolysis, while U2/U5/U6 remain attached to the lariat. The spliced RNA, the lariat, and the snRNPs are all released and destroyed before being recycled.

And hence we get mRNA free of introns and only constituting only of coding introns capped and tailed at the 5’ and 3’ ends respectively.

What happens in RNA splicing?

The first RNA transcribed from a gene’s DNA template must be processed before it becomes a mature messenger RNA (mRNA) that can control protein synthesis in most eukaryotic genes (and some prokaryotic genes).

Most eukaryotic genes (and some prokaryotic genes as well) require processing before the pre-messenger RNA is converted into a mature messenger RNA (mRNA) that can actually be used for synthesizing protein.

The processing of hnRNA to mature mRNA requires 3 steps in total:

• Addition of 7-methyl guanosine at the 5’ end
• Trimming of the 3’ end and addition of a 200 “A” nucleotide tail by an enzyme called Poly A Polymerase.
• Splicing of the introns.

So we see that splicing is only one of the steps of post-transcriptional processing of RNA.

How does RNA splicing work?

Splicing’s biochemical mechanism has been researched in a variety of situations and is now pretty well described.

Introns are eliminated from main transcripts by cleavage at splice sites, which are conserved sequences. Introns have these locations at the 5’- and 3”- ends. The RNA sequence most typically deleted starts with the dinucleotide GU at the 5’-end and finishes with AG at the 3’-end.

Even if a single nucleotide is altered, it can inhibit the entire splicing process; hence conserving the consensus nucleotide sequence is important. Another significant region occurs at the branch point, which may be found anywhere between 18 and 40 nucleotides upstream from an intron’s 3’-end. The adenine at the branch point is always present, while the rest of the sequence is rather weakly preserved.

Splicing is carried out in numerous phases, with tiny nuclear ribonucleoproteins acting as catalysts (snRNPs, commonly called “snurps“).

Also Read:

• Tapeworms characteristics
• Saturated fatty acid
• Are proteins soluble
• Bacterial enzyme example
• Parasitic fungi examples
• Animal cell
• Unique characteristics of arachnids
• Bacteria cell wall types
• Hydrolase enzyme examples
• Receptor protein example

Splicing is the process of removing introns in mRNA.

To the question “Does splicing occur in Prokaryotes?” the answer is vague as it cannot be answered in a  definite manner. Spicing occurs only in non-coding RNA in prokaryotes, the process is something similar to splicing.

According to biological terms, splicing refers to the removal of introns from hnRNA and joining the exons to make the pure mRNA strand.

Does splicing occur in all cells?

Splicing is a process of removal of unnecessary parts of RNA and occurs in all organisms.

The most accustomed mRNA splicing is unique to eukaryotes, while in prokaryotes splicing though rare is found to occur in non-coding RNA i.e usually in tRNA.

In prokaryotes, the genetic material is small in quantity and comprises entirely of coding genes. To remove parts of this transcripted RNA in the name of processing is not only unnecessary but would be considered a wastage of resources in the cell.

Does mRNA splicing occur in prokaryotes?

Splicing of mRNA is a form of post-transcriptional modification.

mRNA splicing is not a phenomenon that occurs in prokaryotes, it is exclusive to eukaryotes. Prokaryotic splicing is found to occur only in non-coding RNA types.

Since prokaryotes have a small gene count, on transcription a pure mRNA strand is produced that does not require any further processing. Unlike eukaryotes that produce heteronuclear RNA on transcription that must be converted to mRNA to be further translated to protein.

Does gene-splicing occur in prokaryotes?

Gene splicing does not occur in prokaryotes as it is simply not required.

Because of its tiny size, bacterial DNA contains coding genes across its whole length. Unlike eukaryotes, which contain extensive chromosomal DNA and non-coding gene segments.

These non-coding regions of the genes are eliminated when they are turned to RNA, leaving just the coding components of the genes. The result of transcription in prokaryotes is mRNA as compared to hnRNA that is further converted to mRNA in eukaryotes after splicing.

Does RNA splicing occur in prokaryotic cells?

Though rare, RNA splicing does occur in prokaryotes.

Unlike in eukaryotes splicing in prokaryotes occurs in non-coding RNA  varieties like in tRNA. Even then the occurrence of splicing is quite a rare phenomenon in prokaryotic cells.

tRNA in prokaryotes is processed via splicing mainly to convert it into its active formylated form. Only in this form can tRNA function and assist in translation from mRNA to protein.

Does post-transcriptional splicing occur in prokaryotes?

Post-transcriptional processing is a feature unique to eukaryotic cells.

Prokaryotic transcription produces a pure mRNA strand that does not require any changes and can be used as it is to translate it to protein. It is specifically hnRNA that is required to undergo splicing to be converted to mRNA.

The entire length of the prokaryotic DNA has coding genes, due to its small size. Unlike eukaryotes that have large chromosomal DNA and parts of the gene are non-coding. On being converted to RNA these non-coding parts are removed to keep only the coding portions of the genes.

Is there alternative splicing in prokaryotes?

Alternative splicing if referred to that of non-coding mRNA does occur in prokaryotes.

Prokaryotic mRNA does not require splicing to remove introns and join the exons, unlike that in eukaryotes. Hence the phenomenon is quite a rarity in prokaryotic cells.

In prokaryotes, splicing can be seen in tRNA or transfer RNS to produce it functional form with the attachment of a formalin derivative. This processing of the tRNA allows it to attach to the mRNA and translate the mRNA to its respective protein molecule.

Does splicing occur in the cytoplasm?

Splicing of hnRNA is a nuclear phenomenon.

Splicing does not occur in the eukaryotic cytoplasm but rather in the nucleus. Another reason it is seen in eukaryotes as prokaryotes do not have a nucleus.

Splicing is a post transcription process i.e it occurs after transcription that itself occurs in the nucleus. The hnRNA produced in transcription is converted to mRNA via splicing in the nucleus itself before moving to the cytoplasmic Golgi bodies for the next part i.e translation.

Where does splicing occur?

Eukaryotic spicing occurs in the nucleus while prokaryotic splicing in the cytoplasm.

In eukaryotes, splicing occurs right after transcription which itself occurs in the nucleus so, the post-transcriptional processing occurs in the nucleus as well after which the mRNA moves into the cytoplasm.

On the other hand, prokaryotic splicing occurs in tRNA and other non-coding RNAs which are found in the cytoplasm, hence the process of splicing occurs in the cytoplasm as well. Also since prokaryotic cells do not have a nucleus, splicing cannot technically occur in the nucleus in prokaryotic cells anyway.

Please click to learn more about Do Prokaryotes Have Golgi.

Also Read:

• Biennial plant example
• Can rna leave the nucleus
• Do prokaryotes have enzymes
• Fibrous protein example
• Are diatoms protists
• Is cell membrane an organelle
• Are cell wall an organelle
• Do plant cells have endoplasmic reticulum
• Turbellaria characteristics
• Is endocytosis hypertonic

Transfer RNA or simply tRNAs are present in prokaryotes.

To answer the question “Do prokaryotes have tRNA?”, the answer is obviously it does. Since all organisms require the help of tRNA to complete protein synthesis it is essential in prokaryotes as well.

tRNA is one of the varieties of RNA molecule that physically links mRNA and the amino acid sequence of the proteins it translates. This is done by the tRNA by transferring an amino acid to the ribosome hence the name.

ALL ABOUT tRNA:

• tRNA, a  type of RNA molecule that is made up of 76- 90 nucleotides approximately.
• tRNA or transfer-RNA was formerly referred to as sRNA or simply put as soluble RNA.
• Every tRNA molecule has two functional areas: a trinucleotide region called the anticodon and a region for attaching a specific amino acid
• Transfer RNA carries an amino acid to an organelle called the ribosome.
• Complementing a 3-nucleotide codon in the transcribed mRNA by a 3-nucleotide anticodon in the tRNA is what results in translation (i.e. formation of protein molecule) based on the mRNA code.
• Hence tRNAs are necessary for the process of translation in both prokaryotes and eukaryotes.
• The D-loop, T loop, variable loop, and anticodon loop are all part of the secondary structure of tRNA that looks like a
• cloverleaf.
•  Through coaxial stacking of the T and D loops, the tRNA folds into an L-shaped tertiary structure.

 Function of tRNA in prokaryotes:

The function of tRNA in prokaryotes is the same as that in other organisms.

The tRNA’s main function is to read nucleotides and convert them into the respective proteins or simply carry out protein synthesis via translation. tRNAs read the mRNA code in the form of 3 letter nucleoside fragments called codons.

A total of 64 3 letter codons are present that read 21 amino acids. Some also start or stop the translation process – called start and stop codons respectively. They are present in specified locations. There are also more than 1 codon coding for the same amino acid.

Eg the codons CGT, CGC, CGA, CGG, AGA, AGG all code the same amino acid Arginine.

Apart from translation, tRNA identifies the enzyme Aminoacyl tRNA synthetase, which grabs certain amino acids from the cytoplasm and transports them to the site of translation.

Why is initiator tRNA formylated in prokaryotes?

Translation Initiator tRNA or simply initiator tRNA is crucial in both eukaryotes and prokaryotes.

By using specialised base pairing between its anticodon triplet CAU and the general initiation codon AUG in the mRNA, tRNA plays a critical role in the commencement of protein synthesis in both prokaryotic and eukaryotic cells.

Protein translation can only start once the initiation complex along with the 30S ribosome unit recognizes the translation start site on the mRNA. This initiator complex comprises of formylmethionine or (fMet-tRNAfMet) and three proteins called initiation factor-1 (IF1), Initiation factor 2 or  IF2 and Initiation Factor or IF3 respectively.

The initiator tRNA formation is a compulsory step the allows to be able to the initiation factors and carry them to the mRNA and start the process of translation altogether. It is only after formylation that the tRNA can recognize the initiator codons on the mRNA.

tRNA processing in prokaryotes:

• tRNA precursors often have additional nucleotides at both their 5′ and 3′ ends, as well as intervening sequences in the centre of the molecule in some cases.
• Additional tRNAs may be included as part of the extra nucleotide sequences if the precursor is multimeric.
• Furthermore, precursors frequently lack the 3′ terminal -CCA sequence seen in all working tRNAs, as well as the entire complement of changed nucleotides that define tRNA structure.
• In various prokaryotic species, tRNA genes can be found in several settings. They are found as single genes in diverse systems,8 in clusters having several tRNA sequences (as many as 21 in Bacillus subtifi),” in the spacer and distal sections of rRNA operons, and in conjunction with protein genes.
• Several tRNA gene transcripts have been discovered as a result of these different forms of gene organisation. As a result, tRNA precursors representing transcripts from a single tRNA gene or clusters of tRNA genes have been discovered.
• Endonucleolytic cleavages, which serve to separate the tRNA sequences from extraneous nucleotide residues or other RNAs, are the key processing events in the development of tRNAs from all types of precursors.
•  If RNaseP is used to do the main cleavage, the mature tRNA’s 5′ terminal is produced. When it comes to monomeric precursors, this is frequently the case.
• Multimeric and polycistronic precursors containing tRNA sequences, on the other hand, are frequently cleaved by different endoribonucleases to produce smaller fragments, which are then further processed to provide the mature tRNA 5′ and 3′ termini.
• In typically developing wild type cells, intact primary transcripts are not found, suggesting that endonucleolytic cleavages occur quickly during or soon after transcription. tRNA precursors can be detected in normal cells under particular conditions, such as when a processing system is overloaded by a high number of transcripts or when a transcript has a poor substrate.
• When a tRNA gene cloned in a bacteriophage or plasmid is injected into bacteria or eukaryotic cells, this is something commonly seen.
• The activity of the endonuclease RNase P can create the 5′ phosphoryl terminal of mature tRNAs from tRNA precursors.

Also Read:

• Does translation occur in the cytoplasm
• Do bacteria have dna
• Is enzyme a catalyst
• Monogenea characteristics
• Polyunsaturated fatty acids examples
• Is cytoplasm an organelle
• Artificial ecosystem example
• Hybrid plant examples
• When does cell division occur
• Is primary transport active