Linked Life Data

12488449

Source:http://linkedlifedata.com/resource/pubmed/id/12488449

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
11
pubmed:dateCreated
2003-3-10
pubmed:databankReference
pubmed:abstractText
Aspartate aminotransferase has been known to undergo a significant conformational change, in which the small domain approaches the large domain, and the residues at the entrance of the active site pack together, on binding of substrates. Accompanying this conformational change is a two-unit increase in the pK(a) of the pyridoxal 5'-phosphate-Lys(258) aldimine, which has been proposed to enhance catalysis. To elucidate how the conformational change is coupled to the shift in the aldimine pK(a) and how these changes are involved in catalysis, we analyzed structurally and kinetically an enzyme in which Val(39) located at both the domain interface and the entrance of the active site was replaced with a bulkier residue, Phe. The V39F mutant enzyme showed a more open conformation, and the aldimine pK(a) was lowered by 0.7 unit compared with the wild-type enzyme. When Asn(194) had been replaced by Ala in advance, the V39F mutation did not decrease the aldimine pK(a), showing that the domain rotation controls the aldimine pK(a) via the Arg(386)-Asn(194)-pyridoxal 5'-phosphate linkage system. The maleate-bound V39F enzyme showed the aldimine pK(a) 0.9 unit lower than that of the maleate-bound wild-type enzyme. However, the positions of maleate, Asn(194), and Arg(386) were superimposable between the mutant and the wild-type enzymes; therefore, the domain rotation was not the cause of the lowered aldimine pK(a) value. The maleate-bound V39F enzyme showed an altered side-chain packing pattern in the 37-39 region, and the lack of repulsion between Gly(38) carbonyl O and Tyr(225) Oeta seemed to be the cause of the reduced pK(a) value. Kinetic analysis suggested that the repulsion increases the free energy level of the Michaelis complex and promotes the catalytic reaction.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
14
pubmed:volume
278
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
9481-8
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:12488449-Aspartate Aminotransferases, pubmed-meshheading:12488449-Aspartic Acid, pubmed-meshheading:12488449-Binding Sites, pubmed-meshheading:12488449-Catalysis, pubmed-meshheading:12488449-Escherichia coli, pubmed-meshheading:12488449-Glycine, pubmed-meshheading:12488449-Hydrogen-Ion Concentration, pubmed-meshheading:12488449-Kinetics, pubmed-meshheading:12488449-Ligands, pubmed-meshheading:12488449-Lysine, pubmed-meshheading:12488449-Malates, pubmed-meshheading:12488449-Models, Chemical, pubmed-meshheading:12488449-Models, Molecular, pubmed-meshheading:12488449-Mutagenesis, Site-Directed, pubmed-meshheading:12488449-Mutation, pubmed-meshheading:12488449-N-Methylaspartate, pubmed-meshheading:12488449-Oxygen, pubmed-meshheading:12488449-Photons, pubmed-meshheading:12488449-Plasmids, pubmed-meshheading:12488449-Protein Binding, pubmed-meshheading:12488449-Protein Conformation, pubmed-meshheading:12488449-Protein Structure, Secondary, pubmed-meshheading:12488449-Protein Structure, Tertiary, pubmed-meshheading:12488449-Spectrophotometry, pubmed-meshheading:12488449-Tyrosine, pubmed-meshheading:12488449-Valine
pubmed:year
2003
pubmed:articleTitle
Conformational change in aspartate aminotransferase on substrate binding induces strain in the catalytic group and enhances catalysis.
pubmed:affiliation
Department of Biochemistry, Osaka Medical College, Takatsuki 569-8686, Japan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't