title: Resistance to beta-lactam antibiotics and its mediation by the sensor domain of the transmembrane BlaR signaling pathway in Staphylococcus aureus.
abstract: Staphylococci, a leading cause of infections worldwide, have devised two mechanisms for resistance to beta-lactam antibiotics. One is production of beta-lactamases, hydrolytic resistance enzymes, and the other is the expression of penicillin-binding protein 2a (PBP 2a), which is not susceptible to inhibition by beta-lactam antibiotics. The beta-lactam sensor-transducer (BlaR), an integral membrane protein, binds beta-lactam antibiotics on the cell surface and transduces the information to the cytoplasm, where gene expression is derepressed for both beta-lactamase and penicillin-binding protein 2a. The gene for the sensor domain of the sensor-transducer protein (BlaR(S)) of Staphylococcus aureus was cloned, and the protein was purified to homogeneity. It is shown that beta-lactam antibiotics covalently modify the BlaR(S) protein. The protein was shown to contain the unusual carboxylated lysine that activates the active site serine residue for acylation by the beta-lactam antibiotics. The details of the kinetics of interactions of the BlaR(S) protein with a series of beta-lactam antibiotics were investigated. The protein undergoes acylation by beta-lactam antibiotics with microscopic rate constants (k(2)) of 1-26 s(-1), yet the deacylation process was essentially irreversible within one cell cycle. The protein undergoes a significant conformational change on binding with beta-lactam antibiotics, a process that commences at the preacylation complex and reaches its full effect after protein acylation has been accomplished. These conformational changes are likely to be central to the signal transduction events when the organism is exposed to the beta-lactam antibiotic.
authors.affiliation: Department of Chemistry, Institute for Drug Design, Wayne State University, Detroit, Michigan 48202-3489, USA.
authors.forename: Dasantila
authors.initials: D
authors.lastname: Golemi-Kotra
authors.forename: Joo Young
authors.initials: JY
authors.lastname: Cha
authors.forename: Samy O
authors.initials: SO
authors.lastname: Meroueh
authors.forename: Sergei B
authors.initials: SB
authors.lastname: Vakulenko
authors.forename: Shahriar
authors.initials: S
authors.lastname: Mobashery
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins; D001665:Binding Sites; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry; D002352:Carrier Proteins / Q000378:metabolism*; D002942:Circular Dichroism; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004252:DNA Mutational Analysis; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000378:metabolism; D005786:Gene Expression Regulation; D006602:Hexosyltransferases; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008239:Lysine / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008958:Models, Molecular; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D013211:Staphylococcus aureus / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D047090:beta-Lactams; D002245:Carbon Dioxide; D012694:Serine; D002244:Carbon; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D008239:Lysine