Peptidyl-transfer RNA hydrolase prevents inhibition of protein synthesis initiation [32]

Abstract

PEPTIDYL-TRNA HYDROLASE (called hydrolase below) catalyses the hydrolysis of peptides from peptidyl-tRNAs that are not bound to ribosomes1,2 but will not hydrolyse amino acyl-tRNA or fMet-tRNAfMet. It is interesting that hydrolase seems to be ubiquitous in nature, it has been found in all cells where it has been sought, including yeast3, bacteria, rat liver and jackbeans4 However, the metabolic role of this enzyme has not been established It is required for normal function, as a mutant strain of Escherichia coli with a temperature-sensitive hydrolase cannot continue protein synthesis at the nonpermissive temperature5 Hydrolase itself is not required for initiation, elongation or termination phases of protein synthesis6 Menninger7 has shown that peptidyl-tRNA, formed on ribosomes, accumulates at nonpermissive temperatures in cells with the temperature-sensitive hydrolase. Hydrolase thus seems to be a scavenger enzyme of peptidyl-tRNAs normally aborted from ribosomes during protein synthesis Of interest now is why peptidyl-tRNA is frequently prematurely released from ribosomes and why protein synthesis is inhibited in the mutant strain with a defective hydrolase5 I report here work on the latter problem and present evidence which indicates that peptidyl-tRNAs accumulate and compete with N-formal-Met tRNAfMet during initiation of protein synthesis. © 1978 Nature Publishing Group.