Altered regulation of the glnRA operon in a Bacillus subtilis mutant that produces methionine sulfoximine-tolerant glutamine synthetase

Abstract

A Bacillus subtilis mutant that produced glutamine synthetase (GS) with altered sensitivity to DL-methionine sulfoximine was isolated. The mutation, designated glnA33, was due to a T·A-to-C·G transition, changing valine to alanine at codon 190 within the active-site C domain. Altered regulation was observed for GS activity and antigen and mRNA levels in a B. subtilis glnA33 strain. The mutant enzyme was 28-fold less sensitive to DL-methionine sulfoximine and had a 13.0-fold-higher K(m) for hydroxylamine and a 4.8- fold-higher K(m) for glutamate than wild-type GS did.