Chapter 18
- X-ray crystallography of the 50S ribosomal subunit has shown that rRNA, but not protein is at the active center of the peptidyl transferase enzyme, which is an inherent activity of the 50S subunit. Several lines of evidence pointed to the conserved residue A2451 as the nucleotide with principal responsibility for catalysis. But Polacek et al. have shown that mutations at residue A2451 do not severely affect peptidyl transferase activity. Mutations at residue 2447, which was also implicated in the mechanism involving A2451, also had an undramatic effect. The authors conclude that the ribosome does not cause transpeptidation by chemical catalysis, but by positioning the substrates properly. (Polecek, N., M. Gaynor, A. Yassin, and A.S. Mankin. 2001. Ribosomal peptidyl transferase can withstand mutations at the putative catalytic nucleotide. Nature 411:498-501)
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