Crystal Structures of the Bacillus licheniformis BS3 Class A β-Lactamase and of the Acyl−Enzyme Adduct Formed with Cefoxitin
| Autor: | Jean-Marie Frère, E. Fonze, Marc Vanhove, Georges Dive, Eric Sauvage, Paulette Charlier |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Models
Molecular Macromolecular Substances Stereochemistry medicine.medical_treatment Static Electricity Substituent Bacillus Crystallography X-Ray Biochemistry Protein Structure Secondary beta-Lactamases Adduct Cefoxitin chemistry.chemical_compound Catalytic Domain Hydrolase polycyclic compounds medicine Bacillus licheniformis Cephamycins chemistry.chemical_classification biology Active site biology.organism_classification Kinetics Enzyme chemistry biology.protein Beta-lactamase medicine.drug |
| Zdroj: | Biochemistry. 41:1877-1885 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi015789k |
| Popis: | The Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common and thoroughly studied cause of antibiotic resistance. Although they escape the hydrolytic activity of the prototypical Staphylococcus aureus beta-lactamase, many cephems are good substrates for a large number of beta-lactamases. However, the introduction of a 7alpha-methoxy substituent, as in cefoxitin, extends their antibacterial spectrum to many cephalosporin-resistant Gram-negative bacteria. The 7alpha-methoxy group selectively reduces the hydrolytic action of many beta-lactamases without having a significant effect on the affinity for the target enzymes, the membrane penicillin-binding proteins. We report here the crystallographic structures of the BS3 enzyme and its acyl-enzyme adduct with cefoxitin at 1.7 A resolution. The comparison of the two structures reveals a covalent acyl-enzyme adduct with perturbed active site geometry, involving a different conformation of the omega-loop that bears the essential catalytic Glu166 residue. This deformation is induced by the cefoxitin side chain whose position is constrained by the presence of the alpha-methoxy group. The hydrolytic water molecule is also removed from the active site by the 7beta-carbonyl of the acyl intermediate. In light of the interactions and steric hindrances in the active site of the structure of the BS3-cefoxitin acyl-enzyme adduct, the crucial role of the conserved Asn132 residue is confirmed and a better understanding of the kinetic results emerges. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|