Glutamine auxotrophs of Bacillus subtilis that overproduce glutamine synthetase antigen have altered conserved amino acids in or near the active site.

A number of mutations within the Bacillus subtilis glutamine synthetase (GS) gene result in altered catalytic properties and overproduction of the GS antigen. The restriction fragments containing mutations from three such mutants were sequenced, and they all had amino acid changes in conserved residues found either within or near sequences contributing to the active site of the Salmonella typhimurium GS.