Page "Ribosome" Paragraph 21

Prokaryotes have 70S ribosomes, each consisting of a small ( 30S ) and a large ( 50S ) subunit.

Their small subunit has a 16S RNA subunit ( consisting of 1540 nucleotides ) bound to 21 proteins.

The large subunit is composed of a 5S RNA subunit ( 120 nucleotides ), a 23S RNA subunit ( 2900 nucleotides ) and 31 proteins.

Affinity label for the tRNA binding sites on the E. coli ribosome allowed the identification of A and P site proteins most likely associated with the peptidyltransferase activity ; labelled proteins are L27, L14, L15, L16, L2 ; at least L27 is located at the donor site, as shown by E. Collatz and A. P.

Czernilofsky.

Additional research has demonstrated that the S1 and S21 proteins, in association with the 3 '- end of 16S ribosomal RNA, are involved in the initiation of translation.