Source:http://linkedlifedata.com/resource/pubmed/id/15895997
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
20
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| pubmed:dateCreated |
2005-5-17
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| pubmed:abstractText |
The beta-lactam antibiotics act through their inhibition of D-alanyl-D-alanine transpeptidases (DD-peptidases) that catalyze the last step of bacterial cell wall synthesis. Bacteria resist beta-lactams by a number of mechanisms, one of the more important of which is the production of beta-lactamases, enzymes that catalyze the hydrolysis of these antibiotics. The serine beta-lactamases are evolutionary descendants of DD-peptidases and retain much of their structure, particularly at the active site. Functionally, beta-lactamases differ from DD-peptidases in being able to catalyze hydrolysis of acyl-enzyme intermediates derived from beta-lactams and being unable to efficiently catalyze acyl transfer reactions of D-alanyl-D-alanine terminating peptides. The class C beta-lactamase of Enterobacter cloacae P99 is closely similar in structure to the DD-peptidase of Streptomyces R61. Previous studies have demonstrated that the evolution of the beta-lactamase, presumably from an ancestral DD-peptidase similar to the R61 enzyme, included structural changes leading to rejection of the D-methyl substituent of the penultimate D-alanine residue of the DD-peptidase substrate. This seems to have been achieved by suitable placement of the side chain of Tyr 221 in the beta-lactamase. We show in this paper that mutation of this residue to Gly 221 produces an enzyme that more readily hydrolyzes and aminolyzes acyclic D-alanyl substrates than glycyl analogues, in contrast to the wild-type beta-lactamase; the mutant is therefore a more efficient DD-peptidase. Molecular modeling showed that the D-alanyl methyl group fits snugly into the space originally occupied by the Tyr 221 side chain and, in doing so, allows the bound substrate to assume a conformation similar to that on the R61 DD-peptidase, which has a hydrophobic pocket for this substituent. Another mutant of the P99 beta-lactamase, the extended spectrum GC1 enzyme, also has space available for a D-alanyl methyl group because of an extended omega loop. In this case, however, no enhancement of activity against D-alanyl substrates with respect to glycyl was observed. Accommodation of the penultimate D-alanyl methyl group is therefore necessary for efficient DD-peptidase activity, but not sufficient.
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| pubmed:grant | |
| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:citationSubset |
IM
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| pubmed:chemical | |
| pubmed:status |
MEDLINE
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| pubmed:month |
May
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| pubmed:issn |
0006-2960
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| pubmed:author | |
| pubmed:issnType |
Print
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| pubmed:day |
24
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| pubmed:volume |
44
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
7543-52
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| pubmed:dateRevised |
2007-11-15
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| pubmed:meshHeading |
pubmed-meshheading:15895997-Binding Sites,
pubmed-meshheading:15895997-Catalysis,
pubmed-meshheading:15895997-Computer Simulation,
pubmed-meshheading:15895997-Enterobacter cloacae,
pubmed-meshheading:15895997-Evolution, Molecular,
pubmed-meshheading:15895997-Glycine,
pubmed-meshheading:15895997-Hydrolysis,
pubmed-meshheading:15895997-Models, Molecular,
pubmed-meshheading:15895997-Sequence Deletion,
pubmed-meshheading:15895997-Serine-Type D-Ala-D-Ala Carboxypeptidase,
pubmed-meshheading:15895997-Thermodynamics,
pubmed-meshheading:15895997-Tyrosine,
pubmed-meshheading:15895997-beta-Lactamases
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| pubmed:year |
2005
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| pubmed:articleTitle |
The D-methyl group in beta-lactamase evolution: evidence from the Y221G and GC1 mutants of the class C beta-lactamase of Enterobacter cloacae P99.
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| pubmed:affiliation |
Department of Chemistry, Wesleyan University, Middletown, Connecticut 06459, USA.
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| pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, N.I.H., Extramural
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