Linked Life Data

15788415

Source:http://linkedlifedata.com/resource/pubmed/id/15788415

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
21
pubmed:dateCreated
2005-5-23
pubmed:databankReference
pubmed:abstractText
Metallo-beta-lactamase IMP-1 is a di-Zn(II) metalloenzyme that efficiently hydrolyzes beta-lactam antibiotics. Wild-type (WT) IMP-1 has a conserved Asp-120(81) in the active site, which plays an important role in catalysis. To probe the catalytic role of Asp-120(81) in IMP-1, the IMP-1 mutants, D120(81)A and D120(81)E, were prepared by site-directed mutagenesis, and various kinetics studies were conducted. The IMP-1 mutants exhibited 10(2)-10(4)-fold drops in k(cat) values compared with WT despite the fact that they contained two Zn(II) ions in the active site. To evaluate the acid-base characteristics of Asp-120(81), the pH dependence for hydrolysis was examined by stopped-flow studies. No observable pK(a) values between pH 5 and 9 were found for WT and D120(81)A. The rapid mixing of equimolar amounts of nitrocefin and all enzymes failed to result in the detection of an anion intermediate of nitrocefin at 650 nm. These results suggest that Asp-120(81) of IMP-1 is not a factor in decreasing the pK(a) for the water bridging two Zn(II) ions and is not a proton donor to the anionic intermediate. In the case of D120(81)E, the nitrocefin hydrolysis product, which shows a maximum absorption at 460 nm, was bound to D120(81)E in the protonated form. The three-dimensional structures of D120(81)A and D120(81)E were also determined at 2.0 and 3.0 A resolutions, respectively. In the case of D120(81)E, the Zn-Zn distance was increased by 0.3 A compared with WT, due to the change in the coordination mode of Glu-120(81)OE1 and the positional shift in the conserved His-263(197) at the active site.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
27
pubmed:volume
280
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
20824-32
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:15788415-Aspartic Acid, pubmed-meshheading:15788415-Binding Sites, pubmed-meshheading:15788415-Catalysis, pubmed-meshheading:15788415-Cephalosporins, pubmed-meshheading:15788415-Conserved Sequence, pubmed-meshheading:15788415-Crystallization, pubmed-meshheading:15788415-Crystallography, X-Ray, pubmed-meshheading:15788415-Hydrogen-Ion Concentration, pubmed-meshheading:15788415-Hydrolysis, pubmed-meshheading:15788415-Kinetics, pubmed-meshheading:15788415-Models, Molecular, pubmed-meshheading:15788415-Molecular Structure, pubmed-meshheading:15788415-Mutagenesis, Site-Directed, pubmed-meshheading:15788415-Recombinant Proteins, pubmed-meshheading:15788415-Serratia marcescens, pubmed-meshheading:15788415-Structure-Activity Relationship, pubmed-meshheading:15788415-Zinc, pubmed-meshheading:15788415-beta-Lactamases
pubmed:year
2005
pubmed:articleTitle
Probing the role of Asp-120(81) of metallo-beta-lactamase (IMP-1) by site-directed mutagenesis, kinetic studies, and X-ray crystallography.
pubmed:affiliation
Department of Structure-Function Physical Chemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-Honmachi, Kumamoto 862-0973, Japan. yyamagu@gpo.kumamoto-u.ac.jp
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't