Thiostrepton, an Inhibitor of 50 S Ribosome Subunit Function

Abstract

Thiostrepton inhibits 14 C-leucine incorporation by intact cells of Bacillus megaterium as well as 14 C-phenylalanine incorporation by a poly U-directed extract of Escherichia coli . Extracts of E. coli which are pretreated by incubation with thiostrepton cannot be reactivated by dialysis to more than 5% of their former activity. The 50 S ribosome subunit appears to be the site of thiostrepton action, since protein-synthesizing activity can be restored to dialyzed pretreated extracts by supplementation with 50 S ribosome subunits but not with 30 S ribosome subunits. This technique also provides a simple sensitive method for detection of the biological activity of very small amounts of 50 S ribosome subunits.