Structural basis of broad-spectrum β-lactam resistance in Staphylococcus aureus

Abstract

Broad-spectrum β-lactam antibiotic resistance in Staphylococcus aureus is a global healthcare burden1,2. In clinical strains, resistance is largely controlled by BlaR13, a receptor that senses β-lactams through the acylation of its sensor domain, inducing transmembrane signalling and activation of the cytoplasmic-facing metalloprotease domain4. The metalloprotease domain has a role in BlaI derepression, inducing blaZ (β-lactamase PC1) and mecA (β-lactam-resistant cell-wall transpeptidase PBP2a) expression3–7. Here, overcoming hurdles in isolation, we show that BlaR1 cleaves BlaI directly, as necessary for inactivation, with no requirement for additional components as suggested previously8. Cryo-electron microscopy structures of BlaR1—the wild type and an autocleavage-deficient F284A mutant, with or without β-lactam—reveal a domain-swapped dimer that we suggest is critical to the stabilization of the signalling loops within. BlaR1 undergoes spontaneous autocleavage in cis between Ser283 and Phe284 and we describe the catalytic mechanism and specificity underlying the self and BlaI cleavage. The structures suggest that allosteric signalling emanates from β-lactam-induced exclusion of the prominent extracellular loop bound competitively in the sensor-domain active site, driving subsequent dynamic motions, including a shift in the sensor towards the membrane and accompanying changes in the zinc metalloprotease domain. We propose that this enhances the expulsion of autocleaved products from the active site, shifting the equilibrium to a state that is permissive of efficient BlaI cleavage. Collectively, this study provides a structure of a two-component signalling receptor that mediates action—in this case, antibiotic resistance—through the direct cleavage of a repressor.

Genome features of a novel hydrocarbonoclastic Chryseobacterium oranimense strain and its comparison to bacterial oil-degraders and to other C. oranimense strains

“…The COTT genome was the only C . oranimense genome containing the bla regulator protein BlaR1 (K02172), which largely controls β-lactam antibiotic resistance 118 and membrane carboxypeptidase (penicillin-binding protein) which would render COTT resistant to penicillin ( Additional file 2: Supplementary Table S18 and S28 ). There were also three phenicol and two bacteriocin genes identified in COTT ( Additional file 2: Table S28 ).…”

Detection of mecA Genes in Hospital-Acquired MRSA and SOSA Strains Associated with Biofilm Formation

“…It has been reported that the resistance of S. aureus to β-lactam antibiotics is controlled by the BlaR13 receptor that senses β-lactams through acylation of its sensor domain, inducing transmembrane signaling and activation of the cytoplasm-oriented metalloprotease domain. This domain induces the expression of blaZ (β-lactamase PC1) and mecA (β-lactam-resistant cell wall transpeptidase PBP2a) [ 80 ], the latter encoding the alternative penicillin-binding protein, PBP2A, which is insensitive to antibiotics. Another reason for resistance is due to additional genetic adjustments to develop a high level of resistance [ 81 ].…”

Molecular Determinants of β-Lactam Resistance in Methicillin-Resistant Staphylococcus aureus (MRSA): An Updated Review

“…In clinical S. aureus strains, the membrane-embedded receptor BlaR1 senses β-lactams through the acylation of its sensor domain [ 55 ], inducing transmembrane signaling and activation of a cytoplasmic-facing zinc metalloprotease domain [ 56 ]. The activated zinc metalloprotease domain then cleaves the repressor protein BlaI [ 57 , 58 ], inducing the expression of β-lactamase [ 59 , 60 ].…”

“… Regulation of blaZ and mecA . The bla or mec gene clusters encode regulatory systems that sense β-lactams on the cell surface through a membrane-embedded sensor–inducer BlaR1 (PDB: 1XA7)/MecR1 (PDB:6O9S) [ 60 ]. The signal generated by β-lactam detection induces the cleavage of a cytoplasmic transcriptional repressor BlaI/MecI.…”