PMID:8519804
| Citation |
Chen, YW, Dekker, EE and Somerville, RL (1995) Functional analysis of E. coli threonine dehydrogenase by means of mutant isolation and characterization. Biochim. Biophys. Acta 1253:208-14 |
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| Abstract |
The oxidation of L-threonine to 2-amino-ketobutyrate, as catalyzed by L-threonine dehydrogenase, is the first step in the major pathway for threonine catabolism in both eukaryotes and prokaryotes. Threonine dehydrogenase of E. coli has considerable amino-acid sequence homology with a number of Zn(2+)-containing, medium-chain alcohol dehydrogenases. In order to further explore structure/function interrelationships of E. coli threonine dehydrogenase, 35 alleles of tdh that imparted a no-growth or slow-growth phenotype on appropriate indicator media were isolated after mutagenesis with hydroxylamine. Within this collection, 14 mutants had single amino-acid changes that were divided into 4 groups: (a) amino-acid changes associated with proposed ligands to Zn2+; (b) a substitution of one of several conserved glycine residues; (c) mutations at the substrate or coenzyme binding site; (d) alterations that resulted in a change of charge near the active site. These findings uncover previously unidentified amino-acid residues that are important for threonine dehydrogenase catalysis and also indicate that the three-dimensional structure of tetrameric E. coli threonine dehydrogenase has considerable similarity with the dimeric horse liver alcohol dehydrogenase. |
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| Keywords |
Alcohol Oxidoreductases/genetics; Alcohol Oxidoreductases/metabolism; Amino Acid Sequence; Escherichia coli/drug effects; Escherichia coli/enzymology; Escherichia coli/genetics; Genes, Bacterial; Hydroxylamine; Hydroxylamines/pharmacology; Molecular Sequence Data; Mutagenesis; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Structure-Activity Relationship; Threonine/metabolism |
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