Mutation Analysis of the Feedback of Escherichia coli K・t 12 and its UseInhibition Site of Aspartokinase in L - Threoni e Production JSBA III Yuri OGAwA - MiyATA

Aspartokinase III (AKIII), one of three isozymes of EScherichia coti K-12, is iilhibited al]esterically by L-lysine. This enzyme is encoded by the lysC gene and has 449 amino acid residues. We analyzed the feedback inhibition site of AKIII by generating yarious 4)ngC mutants in a plasmid yector. These mutants conferred resistance to L-lysine and!or an L-lysine analogue on their host. The inhibitory effects of L-lysine on and heat tolerance of 14 mutant enzymes were examined and DNA sequencing showed that the types of mutants were 12. Two hot spots, amino acid residue positions 318-325 and 345-352, were detected in the C-terminal region of