Biosynthesis of Pseudouridine in Transfer Ribonucleic Acid

Abstract

An enzyme that catalyzes the formation of specific pseudouridine residues in the anticodon region of tRNA has been characterized in extracts of Salmonella typhimurium and Escherichia coli. It has previously been shown that hisT regulatory mutants of S. typhimurium lack the pseudouridine modifications in the anticodon region of histidine and several other tRNA species. This has permitted the development of a simple radiochemical assay for the modification enzyme, based on the release of tritium from hisT tRNA isolated from cells grown in [5-3H]uridine. This enzyme activity is absent from hisT mutants and is relatively heat-labile in extracts from temperature-sensitive hisT mutants, which suggests that the modification enzyme itself is the primary gene product of the hisT gene.