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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
26
|
| pubmed:dateCreated |
1991-8-1
|
| pubmed:abstractText |
The Escherichia coli truncated methionyl-tRNA synthetase (delta MTS) was shown to catalyze alpha-carbon hydrogen-deuterium exchange of L-selenomethionine, L-methionine, L-ethionine, and L-norleucine in the presence of deuterium oxide. The rate of alpha-proton exchange for L-methionine was shown to be linear with respect to delta MTS concentration. The exchange reaction showed saturation kinetics with apparent Km values of 21 and 4 mM in the absence and presence of saturating adenosine concentrations, respectively. As expected, delta MTS did not catalyze alpha-proton exchange of D-methionine since the enzyme has been shown to be specific for L-amino acids. In the absence of enzyme or in the presence of an equivalent concentration of Zn2+, no hydrogen-deuterium exchange was detected. The exchange reaction was not observed with L-methioninol, an analogue of L-methionine lacking the carboxylate group. These results suggest that the alpha-carboxylate group is a requirement for the delta MTS-catalyzed exchange reaction. The E. coli methionyl-tRNA synthetase (MTS) has previously been shown to be a zinc metalloprotein [Posorske, L. H., Cohn, M., Yanagisawa, N., & Auld, D. S. (1979) Biochim. Biophys. Acta 576, 128]. On the basis of the structural and mechanistic information available on MTS, we propose that the enzyme-bound zinc coordinates the carboxylate of the amino acid, while a base on the enzyme is responsible for exchange of the alpha-proton. The role of the enzyme-bound metal is to render the alpha-proton more acidic through coordination of the carboxylate group.(ABSTRACT TRUNCATED AT 250 WORDS)
|
| pubmed:grant | |
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Jul
|
| pubmed:issn |
0006-2960
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
2
|
| pubmed:volume |
30
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
6412-6
|
| pubmed:dateRevised |
2007-11-14
|
| pubmed:meshHeading | |
| pubmed:year |
1991
|
| pubmed:articleTitle |
A novel alpha-proton exchange reaction catalyzed by Escherichia coli methionyl-tRNA synthetase.
|
| pubmed:affiliation |
Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77225.
|
| pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
|