30S ribosomal subunit and 50S ribosomal subunit (30S and 50S subunits)

30S ribosomal subunit and 50S ribosomal subunit Overview

The 30S and 50S ribosomal subunits are the two major structural and functional components of the prokaryotic 70S ribosome, a ribonucleoprotein complex essential for protein synthesis.[1][2][3][9] The **30S subunit** contains 16S rRNA and 21 ribosomal proteins, providing the binding site for messenger RNA (mRNA) and ensuring accurate codon-anticodon pairing during the translation initiation and decoding process.[1][3][9] The **50S subunit** contains 23S and 5S rRNAs and over 30 proteins, housing the peptidyl transferase center and polypeptide exit tunnel, catalyzing peptide bond formation.[1][7] Both subunits closely cooperate during translation: the 30S subunit reads mRNA and initiates translation, while the 50S performs catalysis and elongation of the nascent peptide.[1][7] These subunits are principal targets for many clinically relevant antibiotics, which exploit structural and functional differences between bacterial and eukaryotic ribosomes to selectively inhibit bacterial protein synthesis, presenting them as key therapeutic targets in infectious diseases.[1][5][7]

Mechanism of Action

Inhibition of protein synthesis by binding to 30S or 50S subunits, disrupting mRNA decoding, tRNA positioning, peptide bond formation, or ribosomal translocation[1][5][7] - Misreading of mRNA codons (e.g., aminoglycosides on 30S)[5] - Prevention of peptide bond formation (e.g., chloramphenicol on 50S)[1] - Blockage of exit tunnel for nascent polypeptide (e.g., macrolides on 50S) - Inhibition of translocation (e.g., spectinomycin on 30S)[5]

Biological Functions

Safety Considerations

Interacting Drugs