Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023241 (Legionella)
 6,990 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A metallo-beta-lactamase determinant was cloned from a genomic library of Legionella (Fluoribacter) gormanii ATCC 33297(T) constructed in the plasmid vector pACYC184 and transformed into Escherichia coli DH5alpha, by screening for clones showing a reduced susceptibility to imipenem. The product of the cloned determinant, named FEZ-1, contains a 30-kDa polypeptide and exhibits an isoelectric pH of 7.6. Sequencing revealed that FEZ-1 is a molecular-class B beta-lactamase which shares the closest structural similarity (29.7% of identical residues) with the L1 enzyme of Stenotrophomonas maltophilia, being a new member of the highly divergent subclass B3 lineage. All the residues that in L1 are known to be directly or indirectly involved in coordination of the zinc ions were found to be conserved also in FEZ-1, suggesting that the geometry of zinc coordination in the active site of the latter enzyme is identical to that of L1. Unlike L1, however, FEZ-1 appeared to be monomeric in gel permeation chromatography experiments and exhibited a distinctive substrate specificity with a marked preference for cephalosporins and meropenem. The properties of FEZ-1 overall resembled those of a beta-lactamase previously purified from the same strain of L. gormanii (T. Fujii, K. Sato, K. Miyata, M. Inoue, and S. Mitsuhashi, Antimicrob. Agents Chemother. 29:925-926, 1986) and are as yet unique among class B enzymes, reinforcing the notion that considerable functional heterogeneity can be encountered among members of this class. A system for overexpression of the bla(FEZ-1) gene in E. coli, based on the T7 phage promoter, was also developed.
 ...
PMID:The Legionella (Fluoribacter) gormanii metallo-beta-lactamase: a new member of the highly divergent lineage of molecular-subclass B3 beta-lactamases. 1081 5

Eleven environmental samples from different sources were screened for the presence of metallo-beta-lactamase-producing bacteria by using a selective enrichment medium containing a carbapenem antibiotic and subsequently testing each isolate for production of EDTA-inhibitable carbapenemase activity. A total of 15 metallo-beta-lactamase-producing isolates, including 10 Stenotrophomonas maltophilia isolates, 3 Chryseobacterium spp., one Aeromonas hydrophila isolate, and one Janthinobacterium lividum isolate (a species in which production of metallo-beta-lactamase activity was not previously reported), were obtained from 8 samples. In the J. lividum isolate, named JAC1, production of metallo-beta-lactamase activity was elicited upon exposure to beta-lactams. Screening of a JAC1 genomic library for clones showing a reduced imipenem susceptibility led to the isolation of a metallo-beta-lactamase determinant encoding a new member (named THIN-B) of the highly divergent subclass B3 lineage of metallo-beta-lactamases. THIN-B is most closely related (35.6% identical residues) to the L1 enzyme of S. maltophilia and more distantly related to the FEZ-1 enzyme of Legionella gormanii (27.8% identity) and to the GOB-1 enzyme of Chryseobacterium meningosepticum (24.2% identity). Sequences related to bla(THIN-B), and inducible production of metallo-beta-lactamase activity, were also detected in the J. lividum type strain DSM1522. Expression of the bla(THIN-B) gene in Escherichia coli resulted in decreased susceptibility to several beta-lactams, including penicillins, cephalosporins (including cephamycins and oxyimino cephalosporins), and carbapenems, revealing a broad substrate specificity of the enzyme. The results of this study indicated that metallo-beta-lactamase-producing bacteria are widespread in the environment and identified a new molecular class B enzyme in the environmental species J. lividum.
 ...
PMID:Metallo-beta-lactamase producers in environmental microbiota: new molecular class B enzyme in Janthinobacterium lividum. 1118 69

The bla(FEZ-1) gene coding for the metallo-beta-lactamase of Legionella (Fluoribacter) gormanii ATCC 33297T was overexpressed via a T7 expression system in Escherichia coli BL21(DE3)(pLysS). The product was purified to homogeneity in two steps with a yield of 53%. The FEZ-1 metallo-beta-lactamase exhibited a broad-spectrum activity profile, with a preference for cephalosporins such as cephalothin, cefuroxime, and cefotaxime. Monobactams were not hydrolyzed. The beta-lactamase was inhibited by metal chelators. FEZ-1 is a monomeric enzyme with a molecular mass of 29,440 Da which possesses two zinc-binding sites. Its zinc content did not vary in the pH range of 5 to 9, but the presence of zinc ions modified the catalytic efficiency of the enzyme. A model of the FEZ-1 three-dimensional structure was built.
 ...
PMID:Biochemical characterization of the FEZ-1 metallo-beta-lactamase of Legionella gormanii ATCC 33297T produced in Escherichia coli. 1125 43

The subclass B3 FEZ-1 beta-lactamase produced by Fluoribacter (Legionella) gormanii is a Zn(II)-containing enzyme that hydrolyzes the beta-lactam bond in penicillins, cephalosporins, and carbapenems. FEZ-1 has been extensively studied using kinetic, computational modeling and x-ray crystallography. In an effort to probe residues potentially involved in substrate binding and zinc binding, five site-directed mutants of FEZ-1 (H121A, Y156A, S221A, N225A, and Y228A) were prepared and characterized using metal analyses and steady state kinetics. The activity of H121A is dependent on zinc ion concentration. The H121A monozinc form is less active than the dizinc form, which exhibits an activity similar to that of the wild type enzyme. Tyr156 is not essential for binding and hydrolysis of the substrate. Substitution of residues Ser221 and Asn225 modifies the substrate profile by selectively decreasing the activity against carbapenems. The Y228A mutant is inhibited by the product formed upon hydrolysis of cephalosporins. A covalent bond between the side chain of Cys200 and the hydrolyzed cephalosporins leads to the formation of an inactive and stable complex.
 ...
PMID:Probing the specificity of the subclass B3 FEZ-1 metallo-beta-lactamase by site-directed mutagenesis. 1515 11