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#prokaryotic ribosome

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Translation Basics

Large subunit rRNA catalyzing peptidyl transferase in prokaryotes is

Peptidyl transferase center that catalyzes peptide bond formation resides in large subunit rRNA, not proteins. In prokaryotes, domain V of 23S rRNA folds into catalytic crevice containing conserved A-loop and P-loop positioning CCA ends of A-site and P-site tRNAs for nucleophilic attack of alpha-amino on peptidyl ester. Crystallographic studies reveal no protein within 18 angstroms of active site. Mutation of key 23S adenines abolishes activity while protein removal retains catalysis. Equivalent in eukaryotes is 28S rRNA, confirming ribosome is ribozyme.

Ref: Watson Molecular Biology of the Gene, 7th ed., Chapter 15, 23S rRNA as peptidyl transferase ribozyme

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Translation Basics

Prokaryotic ribosome is

Prokaryotic ribosome sediments at 70S, consisting of small 30S subunit with 16S rRNA and 21 proteins and large 50S subunit with 23S plus 5S rRNAs and 33 proteins. S values are not additive because shape influences hydrodynamic behavior. 70S ribosome decodes bacterial mRNAs containing Shine-Dalgarno sequences, sensitive to antibiotics like chloramphenicol and tetracycline targeting bacterial-specific features. Cytosolic eukaryotic ribosome is larger at 80S, while mammalian mitochondrial ribosome is 55S, illustrating evolutionary divergence from bacterial ancestor despite shared ancestry. This refined regulation supports accurate ribosomal assembly, quality control and translational fidelity under diverse physiological conditions and growth states.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 6, Bacterial 70S ribosome composition 30S plus 50S

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