Biochemical and regulatory properties of Escherichia coli K-12 hisT mutants

Abstract

E. coli K-12 hisT mutants were isolated and their properties were studied. These mutants are derepressed for the histidine operon, map close to the purF locus at .apprx. 49.5 min on the E. coli linkage map and lack pseudouridylate synthetase activity. The defect in this enzyme leads to the absence of pseudouridines in the anticodon loop of several tRNA species, as evidenced by the altered elution profile on reversed-phase chromatography and resistance to amino acid analogs. The hisT mutants studied have a reduced growth rate that appears to be linked to hisT, although it is not known whether it is due to the same mutation. The normal generation time can be restored by supplementing the medium with adenine, uracil and isoleucine.