7 Ribosomal RNA Function:16S, 23S, 28S And Detailed Facts

The most common type of RNA present in most cells is ribosomal RNA or rRNA. Let us explore more about their functions and detailed facts around it.

  • The main function of ribosomal RNA is protein synthesis by binding with mRNA and tRNA and ensure that it is correctly translated into proteins.
  • The rRNA molecule has substantial coiling. Its name comes from the fact that it joins with proteins to create the small and large subunits of the ribosome.
  • It makes up around 80% of the cell’s overall RNA.
  • The rRNA molecules control the catalytic steps of protein synthesis, which involve combining amino acids to create protein molecules.
  • Because of its role as a catalytic RNA, rRNA is often referred to as a ribozyme or ribozyme.
  • The internal loops and helices of rRNA’s particular three-dimensional shape, which forms the A, P, and E sites in the ribosome, enable it to function.
  • The A site binds an incoming tRNA that has been charged with an amino acid while the P site is for binding a developing polypeptide. Before leaving the ribosome, the tRNA temporarily binds to the E site during the formation of peptide bonds.

Let us discuss major functions of 23 S Ribosomal RNA, 28 S Ribosomal RNA, 5 S Ribosomal RNA, 16 S Ribosomal RNA, 18 S Ribosomal RNA along with the function of Ribosomal RNA in translation and protein synthesis.

23S Ribosomal RNA function

23S ribosomal RNA forms peptide bond during translation process. Let us explore more about the function of 23 S rRNA.

Some of the major function of 23 S Ribosomal RNA are listed below:

  • The key functional role of rRNAs in the translation process is peptide bond formation, which is mainly catalysed by the 23 S rRNA.
  • The peptidyl transferase center (PTC) is made up of 23 S rRNA, a major subunit (50 S) of the bacterial/archean ribosome that is 2,904 nucleotides long (in E. coli).
  • In the P site of the large ribosomal subunit, the 23 S rRNA sites (G 2252, A 2451, U 2506 and U 2585) play a crucial role in tRNA binding.
  • Six primary structural domains make up the 23 S-like ribosomal RNAs (rRNA), which are held together by long-distance base pairing interactions. One of these that has remained among the most highly conserved throughout evolution is domain IV, which suggests that it is essential for protein synthesis at some point.

28S Ribosomal RNA function

28S rRNA is one of the structural and fundamental part of all eukaryotes. Let us discuss some of its functions in detail.

Some of the major function of 28 S Ribosomal RNA are listed below:

  • 28 S rRNA act as structural rRNA large subunit of eukaryotic cytoplasmic ribosomes.
  • The 28 S rDNA genes are responsible for producing 28 S rRNA. Molecular analysis is utilized to build phylogenetic trees using the relationship of the sequences from these genes.
  • Typically, the 28 S rRNA is 4000-5000 nucleotides long. Using hidden break technique, some eukaryotes separate their 28 S RNA into two parts before gathering both into the ribosome. 

5S Ribosomal RNA function

All species except for fungi and animals, include 5S rRNA (ribosomal RNA). Let us get to know more about the functions and facts.

Listed below are the major functions of 5S rRNA:

  • 5 S rRNA is the fundamental part of the larger ribosomal subunit. The molecular weight and length of 5 S rRNA are around 40 kDa and 120 nucleotide, respectively.
  • By stabilizing a ribosome structure, 5 S rRNA is believed to improve protein synthesis.
  • 5 S rRNA was a prime choice for a molecular phylogenetic marker due to its size and widespread distribution, which allowed RNA sequencing using direct techniques.
  • The rate of protein synthesis is decreased and cell fitness is adversely affected more severely in Escherichia coli when the 5 S rRNA gene is deleted than when similar numbers of copies of the other (16 S and 23 S) rRNA genes are deleted.
  • The 5 S rRNA functions as a physical transducer of information, enabling communication between the many functional centers and managing the numerous processes the ribosome catalyses.
  • Crystallographic researches reveal that the central protuberance of the larger subunit and other proteins, including the 5 S rRNA-binding proteins, are involved in the binding of tRNAs.

16S Ribosomal RNA function

The small subunit of bacterial ribosome is made of 30 S subunit, including 16 S rRNA. Some functions of 16 S rRNA is given below.

The major functions of 16 S Ribosomal RNA are listed below:

  • The 16 S rRNA in bacteria has 5–10 copies, which makes the detection incredibly sensitive.
  • The 16 S rRNA gene’s internal structure consists of variable and conserved sections.
  • They interact with 23 S and aid in the fusion of 50 S and 30 S ribosomal subunits.
  • A reverse SD(Shine–Dalgarno  sequence) sequence is included at the 3′ end, which is employed to bind the mRNA’s AUG codon (initiation). The 3′ terminal of the 16 S rRNA in combination with S1 and S21 was observed to be related to the beginning of protein synthesis.
  • The phenotypic methods of identifying bacteria in microbiology can be quickly and inexpensively done by 16 S rRNA sequencing.

18S Ribosomal RNA function

18 S rRNA is a small subunit (SSU) of 40 S rRNA of eukaryotic cell. Let us discuss its functions in detail.

Listed below are major functions of 18 S rRNA:

  • One of the fundamental parts of all eukaryotic cells is the 18 S rRNA, which serves as the structural RNA for the fairly small eukaryotic cytoplasmic ribosome.
  • In the 40 S ribosomal subunit’s 18 S rRNA serves as the active site of protein synthesis.
  • It is assumed that an increases in 18 S rRNA is proportional to the increases in ribosomes, which result in the increase in the volume of RNA transcription and protein synthesis.
  • Further research into the impact of antioxidant supplements on cataract prevention may use 18 S rRNA as an appropriate biomarker for tracking the synthesis of proteins, including antioxidant enzymes.
  • In complicated biological combinations, including as samples taken from the environment and the gut, 18 S rRNA gene sequencing is frequently used to locate, categorize, and quantify bacteria.
  • For the analysis of the genetic diversity and evolutionary relationships of eukaryotes, a phylogenetic tree can be created using different eukaryotic 18 S rRNA gene sequences.

Ribosomal RNA function in translation

Every stage of the translation process, requires the participation of rRNA. Let us explore more about the role of rRNA in translation.

Listed below shows major functions of rRNA in translation:

  • In the cytoplasm, ribosomes read the nucleotide sequence in segments of three bases known as codons using messenger RNA to transport the genetic information encoded in DNA.
  • Over 60% of ribosome’s weight is made up of ribosomal RNA, which is essential for all of the activities of ribosomes, including facilitating the formation of peptide bonds between two amino acids and binding to mRNA and tRNA.
Structure of ribosome showing different subunit and their fundamental rRNA types.
  • Codons are formed by triplets of nucleotides which are adenine, guanine, cytosine and uracil. These four nucleotides by combining forms total 64 codon. Each codon is denoted with single amino acids. Each codon forms the protein sequence by making polypeptide chain.
  • The Shine-Dalgarno (SD) sequence in mRNA is base paired with the 16 S rRNA to start prokaryotic translation.
  • SD sequence is 6-10 nucleotide long and is present at the upstream of the AUG start codon. It binds with rRNA and enables the start codon to be localized within the ribosome.
  • The larger ribosomal subunit is also recruited as a result of this contact, which is mediated by other proteins and the first codon is then translated as a result.

Ribosomal RNA function in protein synthesis

Protein synthesis occurs at specific locations in ribosomes within a cell. Let us discuss the function of ribosomal RNA in protein synthesis.

The major functions of Ribosomal RNA in protein synthesis are listed below:

  • The precise amount of ribosomes in a cell varies according to how active that cell is in making proteins.
  • A non-coding RNA called rRNA aids in the formation of ribosomes, the cell organelle responsible for protein synthesis. Ribosomal RNA can be either little or huge when encoded.
  • Once assembled in the appropriate position, these small and big rRNAs join forces with ribosomal proteins to form ribosomal subunits that are used to synthesize proteins.
  • Through interactions with the core, proteins found in the ribosome help to maintain this structure.
  • In the nucleus, at particular locations known as nucleoli, ribosomal RNA is translated. These are spherical, dense structures that develop around rRNA-coding genes.
  • Through ribosomal protein sequestration, nucleoli are also essential for the ultimate synthesis of ribosomes.
  • During protein synthesis, rRNA binds with both mRNA and tRNA and is a crucial factor in determining how well mRNA sequences are translated. 


To wrap up this post, we can conclude that rRNA plays multiple functions as it is diverse in type. Ribosomal RNA mainly focus in protein synthesis by interacting with mRNA and tRNA. 5 S, 23 S, 16 S, 28 S are present in large and small subunits of ribosomes of eukaryotic and prokaryotic cell and performs various functions.

Read more about Can Fusion Be Controlled.

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