Function of the conserved triad residues in the class C beta-lactamase from Citrobacter freundii GN346.
The conserved KTG triad in the class C beta-lactamase from Citrobacter freundii GN346 was examined as to its function by means of site-directed mutagenesis. The following conversions were performed; Lys-315 to arginine, alanine or glutamic acid, Thr-316 to valine, and Gly-317 to alanine, proline or isoleucine. The resultant mutant enzymes revealed that a basic amino acid at position 315 and a small uncharged residue at position 317 are essential for the enzyme activity, but a hydroxyl group at residue 316 is not required for the enzymatic catalysis. The kinetic properties of the purified Arg-315 and Val-316 enzymes provided information on the function of these residues.
Tsukamoto
K
K
Division of Microbial Chemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Nishida
N
N
Tsuruoka
M
M
Sawai
T
T
D000596:Amino Acids / Q000235:genetics; D001665:Binding Sites; D002511:Cephalosporins / Q000494:pharmacology; D002954:Citrobacter / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D010406:Penicillins / Q000494:pharmacology; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics*
D000596:Amino Acids; D002511:Cephalosporins; D010406:Penicillins; D001618:beta-Lactamases