Premium
The kinetic properties of the carboxy terminal domain of the Bacillus licheniformis 749/I BlaR penicillin‐receptor shed a new light on the derepression of β‐lactamase synthesis
Author(s) -
Duval Valérie,
Swinnen Marc,
Lepage Sophie,
Brans Alain,
Granier Benoît,
Franssen Christine,
Frère JeanMarie,
Joris Bernard
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03520.x
Subject(s) - biology , bacillus licheniformis , penicillin , biochemistry , derepression , acylation , escherichia coli , microbiology and biotechnology , antibiotics , bacteria , psychological repression , gene expression , bacillus subtilis , gene , genetics , catalysis
Summary To study the properties of the BlaR penicillin‐receptor involved in the induction of the Bacillus licheniformis β‐lactamase, the water‐soluble carboxy terminal domain of the protein (BlaR‐CTD) was overproduced in the periplasm of Escherichia coli JM105 and purified to protein homogeneity. Its interactions with various β‐lactam antibiotics were studied. The second‐order acylation rate constants k 2 /K′ ranged from 0.0017 to more than 1 µM −1 s −1 and the deacylation rate constants were lower than 4 × 10 −5 s −1 . These values imply a rapid to very rapid formation of a stable acylated adduct. BlaR‐CTD is thus one of the most sensitive penicillin‐binding proteins presently described. In the light of these results, the kinetics of β‐lactamase induction in Bacillus licheniformis were re‐examined. When starting with a rather high cell density, a good β‐lactamase substrate such as benzylpenicillin is too sensitive to β‐lactamase‐mediated hydrolysis to allow full induction. By contrast, a poor β‐lactamase substrate (7‐aminocephalosporanic acid) can fully derepress β‐lactamase expression under conditions where interference of the antibiotic with cell growth is observed. These results suggest that acylation of the penicillin receptor is a necessary, but not sufficient, condition for full induction.