Linked Life Data

11940588

Source:http://linkedlifedata.com/resource/pubmed/id/11940588

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
27
pubmed:dateCreated
2002-7-1
pubmed:abstractText
The L1 metallo-beta-lactamase from Stenotrophomonas maltophilia is unique among this class of enzymes because it is tetrameric. Previous work predicted that the two regions of important intersubunit interaction were the residue Met-140 and the N-terminal extensions of each subunit. The N-terminal extension was also implicated in beta-lactam binding. Mutation of methionine 140 to aspartic acid results in a monomeric L1 beta-lactamase with a greatly altered substrate specificity profile. A 20-amino acid N-terminal deletion mutant enzyme (N-Del) could be isolated in a tetrameric form but demonstrated greatly reduced rates of beta-lactam hydrolysis and different substrate profiles compared with that of the parent enzyme. Specific site-directed mutations of individual N terminus residues were made (Y11S, W17S, and a double mutant L5A/L8A). All N-terminal mutant enzymes were tetramers and all showed higher K(m) values for ampicillin and nitrocefin, hydrolyzed ceftazidime poorly, and hydrolyzed imipenem more efficiently than ampicillin in contrast to wild-type L1. Nitrocefin turnover was significantly increased, probably because of an increased rate of breakdown of the intermediate species due to a lack of stabilizing forces. K(m) values for monomeric L1 were greatly increased for all antibiotics tested. A model of a highly mobile N-terminal extension in the monomeric enzyme is proposed to explain these findings. Tetrameric L1 shows negative cooperativity, which is not present in either the monomer or N-terminal deletion enzymes, suggesting that the cooperative effect is mediated via N-terminal intersubunit interactions. These data indicate that while the N terminus of L1 is not essential for beta-lactam hydrolysis, it is clearly important to its activity and substrate specificity.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
277
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
24744-52
pubmed:dateRevised
2003-11-14
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Characterization of monomeric L1 metallo-beta -lactamase and the role of the N-terminal extension in negative cooperativity and antibiotic hydrolysis.
pubmed:affiliation
Department of Pathology and Microbiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom. A.M.Simm@bristol.ac.uk
pubmed:publicationType
Journal Article