Discrete steps in sensing of beta-lactam antibiotics by the BlaR1 protein of the methicillin-resistant Staphylococcus aureus bacterium.
Chemical sensing by cell-surface receptors to effect signal transduction is a ubiquitous biological event. Despite extensive structural biochemical study, detailed knowledge of how signal transduction occurs is largely lacking. We report herein a kinetic and structural study, obtained by stopped-flow IR spectroscopy, of the activation of the BlaR1 receptor of the Staphylococcus aureus bacterium by beta-lactam antibiotics. The cell-surface BlaR1 receptor alerts the bacterium to the presence of beta-lactam antibiotics, resulting in expression of the gene for a beta-lactamase enzyme. This enzyme hydrolytically destroys the remaining beta-lactam antibiotics. IR spectroscopic interrogation of the beta-lactam-BlaR1 receptor reaction has allowed the simultaneous measurement of the chemical events of receptor recognition of the beta-lactam and the characterization of the conformational changes in the BlaR1 receptor that result. The key chemical events in beta-lactam recognition are serine acylation and subsequent irreversible decarboxylation of the BlaR1 active site lysine carbamate. Both events are observed by stopped-flow IR kinetics and (13)C isotope-edited IR spectroscopy. The secondary structural changes in the BlaR1 receptor conformation that occur as a consequence of this acylation/decarboxylation are predicted to correlate to the signal transduction event accomplished by this receptor.
Thumanu
Kanjana
K
School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
Cha
Jooyoung
J
Fisher
Jed F
JF
Perrins
Richard
R
Mobashery
Shahriar
S
Wharton
Christopher
C
D000215:Acylation; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D016106:Methicillin Resistance; D046915:Penicillin-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D013211:Staphylococcus aureus; D013696:Temperature; D047090:beta-Lactams / Q000737:chemistry* / Q000378:metabolism
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D047090:beta-Lactams