title: Studies of the repressor (BlaI) of beta-lactamase synthesis in Staphylococcus aureus.
abstract: Purified BlaI, the putative repressor of the beta-lactamase operon in Staphylococcus aureus, binds specifically to two regions of dyad symmetry (operators) located in the blaZ-blaR1 intergenic region. BlaI binds with similar affinity to the two regions and to the related sequence upstream of the mec gene found in methicillin-resistant strains of S. aureus, providing physical evidence for the cross-talk previously observed between these systems. A change from a lysine in the N-terminus of BlaI to an alanine or deletion of the C-terminal 23 amino acids severely reduces its DNA-binding ability, demonstrating the functional importance of both the N- and C-termini. An operator DNA-protein complex observed with crude cell lysates from repressed cells, indistinguishable from that observed with purified BlaI, was eliminated by induction of the beta-lactamase operon. Furthermore, BlaI is proteolytically cleaved in response to the addition of inducer in a blaR1-dependent manner, providing primary evidence for the molecular basis of induction. Thus, BlaI is shown to be the repressor of the beta-lactamase system.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: P D
authors.initials: PD
authors.lastname: Gregory
authors.forename: R A
authors.initials: RA
authors.lastname: Lewis
authors.forename: S P
authors.initials: SP
authors.lastname: Curnock
authors.forename: K G
authors.initials: KG
authors.lastname: Dyke
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism*; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D065093:beta-Lactamase Inhibitors; D010450:Endopeptidases; D001618:beta-Lactamases