THE GDHA1 POINT MUTATION IN ESCHERICHIA-COLI K12 CLR207 ALTERS A KEY LYSINE RESIDUE OF GLUTAMATE-DEHYDROGENASE

gdhA1 is a spontaneous mutant of Escherichia coli that causes complete loss of activity of the NADP-specific glutamate dehydrogenase (GDH) e ncoded by the gdhA gene. The gdhA1 mutational site has been identified by recombinational mapping, polymerase chain reaction (PCR) amplifica tion and DNA sequencing, as an A to G transition at nucleotide 274 of the gdhA coding sequence, resulting in an amino acid change of lysine 92 to glutamic acid. The mutant enzyme forms hybrid hexamers with a wi ld-type GDH, providing a useful system for analysis of conformational integrity of mutational variants.