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Structural and Kinetic Insights into the "Ceftazidimase" Behavior of the Extended-Spectrum β-Lactamase CTX-M-96.
- Source :
-
Biochemistry [Biochemistry] 2015 Aug 18; Vol. 54 (32), pp. 5072-82. Date of Electronic Publication: 2015 Aug 10. - Publication Year :
- 2015
-
Abstract
- Diversification of the CTX-M β-lactamases led to the emergence of variants responsible for decreased susceptibility to ceftazidime, like the Asp240Gly-harboring "ceftazidimases". We solved the crystallographic structure of the Asp240Gly variant CTX-M-96 at 1.2 Å and evaluated the role of Asp240 in the activity toward oxyimino-cephalosporins through simulated models and kinetics. There seem to be subtle changes in the conformation of the active site cavity of CTX-M-96, compared to enzyme variants harboring the Asp240, and these small rearrangements could be due to localized shifts in the environment of the β3 strand. According to the crystallographic evidence, CTX-M-96 presents a "compact" active site, which in spite of its reduced cavity seems to allow the proper interaction with oxyimino-cephalosporins, as suggested by simulated models. The term "ceftazidimases" that is currently applied for the Asp240Gly-harboring CTX-M variants should be used carefully. Structural differences between CTX-M harboring the Asp240Gly mutation (and also probably others like those at Pro167) do not seem to be conclusive to determine the "ceftazidimase" behavior observed in vivo, which is in turn partially supported by the mild improvement in the catalytic efficiency toward ceftazidime by CTX-M-96 and similar enzymes, compared to "parental" Asp240-harboring variants. In addition, it is observed that alterations in OmpF expression could act synergistically with CTX-M-96 for yielding clinical resistance toward ceftazidime. We therefore propose that the observed resistance in vivo is due to the sum of synergic mechanisms, and the term "cefotaximases associated with ceftazidime resistance" could be conveniently used to describe CTX-M harboring the Asp240Gly substitution.
- Subjects :
- Amino Acid Substitution
Bacterial Proteins genetics
Catalytic Domain
Ceftazidime pharmacology
Cephalosporin Resistance genetics
Crystallography, X-Ray
Genes, Bacterial
Genetic Variation
Kinetics
Klebsiella pneumoniae drug effects
Klebsiella pneumoniae genetics
Models, Molecular
Protein Structure, Secondary
Protein Structure, Tertiary
Recombinant Proteins chemistry
Recombinant Proteins genetics
Recombinant Proteins metabolism
beta-Lactamases genetics
Bacterial Proteins chemistry
Bacterial Proteins metabolism
Ceftazidime metabolism
Klebsiella pneumoniae enzymology
beta-Lactamases chemistry
beta-Lactamases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1520-4995
- Volume :
- 54
- Issue :
- 32
- Database :
- MEDLINE
- Journal :
- Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 26228623
- Full Text :
- https://doi.org/10.1021/acs.biochem.5b00313