Multigenic control of ribosomal properties associated with cycloheximide sensitivity in Neurospora crassa

Abstract

IT has been shown by McKeehan and Hardesty¹ that, during protein synthesis by 80S ribosomes, cycloheximide selectively inhibits movement of peptidyl-tRNA from the acceptor to the donor site, and that the coupled hydrolysis of GTP, catalysed by the soluble factor T-II in combination with the ribosomes, is not affected. They proposed that cycloheximide might inhibit protein synthesis by occupying sites on the ribosomes usually available for peptidyl-tRNA. As direct association of the T-II catalysed reaction with translocation has not so far been demonstrated, and GTP hydrolysis by T-II is not inhibited by cycloheximide, it is probable that sensitivity to cycloheximide is entirely associated with ribosomes. This was first proposed by Siegel and Sisler² on the basis of species specific differences in the sensitivity to cycloheximide in yeasts and later supported by the work of Wilkie and his associates³. In the latter case a number of cycloheximide resistant mutants have been studied in vitro; one of these mutants, having a low level of resistance, seemed to have altered ribosomes.