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8RG2

Structure of BlaC from Mycobacterium tuberculosis at pH 8

Summary for 8RG2
Entry DOI10.2210/pdb8rg2/pdb
DescriptorBeta-lactamase, GLYCEROL (3 entities in total)
Functional Keywordsfree form structure of blac from mycobacterium tuberculosis at ph 8, hydrolase
Biological sourceMycobacterium tuberculosis
Total number of polymer chains1
Total formula weight28364.82
Authors
Sun, J.,Bruenle, S.,Ubbink, M. (deposition date: 2023-12-13, release date: 2024-08-28)
Primary citationSun, J.,Boyle, A.L.,Brunle, S.,Ubbink, M.
A low-barrier proton shared between two aspartates acts as a conformational switch that changes the substrate specificity of the beta-lactamase BlaC.
Int.J.Biol.Macromol., 278:134665-134665, 2024
Cited by
PubMed Abstract: Serine β-lactamases inactivate β-lactam antibiotics in a two-step mechanism comprising acylation and deacylation. For the deacylation step, a water molecule is activated by a conserved glutamate residue to release the adduct from the enzyme. The third-generation cephalosporin ceftazidime is a poor substrate for the class A β-lactamase BlaC from Mycobacterium tuberculosis but it can be hydrolyzed faster when the active site pocket is enlarged, as was reported for mutant BlaC P167S. The conformational change in the Ω-loop of the P167S mutant displaces the conserved glutamate (Glu166), suggesting it is not required for deacylation of the ceftazidime adduct. Here, we report the characterization of wild type BlaC and BlaC E166A at various pH values. The presence of Glu166 strongly enhances activity against nitrocefin but not ceftazidime, indicating it is indeed not required for deacylation of the adduct of the latter substrate. At high pH wild type BlaC was found to exist in two states, one of which converts ceftazidime much faster, resembling the open state previously reported for the BlaC mutant P167S. The pH-dependent switch between the closed and open states is caused by the loss at high pH of a low-barrier hydrogen bond, a proton shared between Asp172 and Asp179. These results illustrate how readily shifts in substrate specificity can occur as a consequence of subtle changes in protein structure.
PubMed: 39134195
DOI: 10.1016/j.ijbiomac.2024.134665
PDB entries with the same primary citation
Experimental method
X-RAY DIFFRACTION (1.8 Å)
Structure validation

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PDB entries from 2024-11-20

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