Streptomyces albus G serine beta-lactamase. Probing of the catalytic mechanism via molecular modelling of mutant enzymes.
In previous studies, several amino acids of the active site of class A beta-lactamases have been modified by site-directed mutagenesis. On the basis of the catalytic mechanism proposed for the Streptomyces albus G beta-lactamase [Lamotte-Brasseur, Dive, Dideberg, Charlier, Frère & Ghuysen (1991) Biochem. J. 279, 213-221], the influence that these mutations exert on the hydrogen-bonding network of the active site has been analysed by molecular mechanics. The results satisfactorily explain the effects of the mutations on the kinetic parameters of the enzyme's activity towards a set of substrates. The present study also shows that, upon binding a properly structured beta-lactam compound, the impaired cavity of a mutant enzyme can readopt a functional hydrogen-bonding-network configuration.
Lamotte-Brasseur
J
J
Centre d'Ingénierie des Protéines, Université de Liège, Sart tilman, Belgium.
Jacob-Dubuisson
F
F
Dive
G
G
Frère
J M
JM
Ghuysen
J M
JM
D000595:Amino Acid Sequence; D001665:Binding Sites; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D016296:Mutagenesis; D010406:Penicillins / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D013302:Streptomyces / Q000201:enzymology*; D013379:Substrate Specificity; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D010406:Penicillins; D001618:beta-Lactamases