Disease relevance of tdcB

• The tdcB and tdcC genes of the tdcABC operon of Escherichia coli encode threonine dehydratase and a threonine-serine permease, respectively [1].
• Metabolic redirection of carbon flow toward isoleucine by expressing a catabolic threonine dehydratase in a threonine-overproducing Corynebacterium glutamicum [2].
• Recently, the anaerobic expression of the tdc operon was found to be fortuitously induced in the presence of glucose by a heterologous gene isolated from the Gram-positive anaerobe Clostridium butyricum [3].

High impact information on tdcB

• The 987-base-pair coding region of the tdc gene of Escherichia coli K-12 encoding biodegradative threonine dehydratase [Tdc; L-threonine hydro-lyase (deaminating), EC 4.2.1.16], previously cloned in this laboratory, was sequenced [4].
• Although the purified enzyme was shown to contain tryptophan, no tryptophan codon was found in the tdc reading frame [4].
• This supports a novel mechanism of transcription for the tdc operon, whose promoter lacks any recognizable sigma binding sites [5].
• Examination of the CRP binding site of the tdc promoter revealed that it was located 43.5 bp upstream of the transcription initiation site [3].
• This indicates that the other tdc regulators, TdcA and TdcR, govern anaerobic transcription activation by CRP [3].

Chemical compound and disease context of tdcB

• The synthesis of inducible biodegradative threonine dehydratase of Escherichia coli increased several-fold in the presence of the DNA gyrase inhibitors, nalidixic acid and coumermycin [6].

Biological context of tdcB

• Transcriptional analysis with S1 nuclease indicated two distinct transcription start sites upstream of the tdcB gene in regions previously identified as promoterlike elements P1 and P2 [7].
• The tdc genes and ORFX showed similar codon usage and, in analogy with other bacterial genes, showed codon usage typical for genes expressed at an intermediate level [7].
• The data suggest that P1, and not P2, is necessary for tdc gene expression, and that the DNA sequences coding for the 32 KD polypeptide and threonine dehydratase are part of a single transcriptional unit [8].
• Deletion of the potential CAP-binding site from P1 prevented tdc gene expression [8].
• A 936-base pair open reading frame was found between P1 and the tdc coding region, which produced a polypeptide of about 32 kilodaltons [8].

Associations of tdcB with chemical compounds

• We studied the effects of introducing two different threonine dehydratase genes into this threonine-producing system to gauge their effects on isoleucine production [2].
• One of the products encoded by the tdc operon, TdcE, has recently been shown to be a 2-keto acid formate-lyase (C. Hesslinger, S. A. Fairhurst, and G. Sawers, Mol. Microbiol. 27:477-492, 1998) that can accept pyruvate as an enzyme substrate [9].

Other interactions of tdcB

• A computer-assisted sequence analysis revealed no similarity among the tdcB, tdcC, and ORFX polypeptides, and a search of the GenBank database failed to detect similarity with any other known proteins [7].
• Interestingly, multicopy tdcA+ plasmids introduced into tdcR mutant strains completely restored tdc expression [10].
• Since close linkage of rnpB and tdc is found in various strains of E. coli K-12, the rnpB gene should be mapped at 68 min rather than 70 min [11].
• The biodegradative threonine dehydratase (tdc) operon was mapped at 68 min on the Escherichia coli K-12 chromosome [12].

Analytical, diagnostic and therapeutic context of tdcB

• Molecular cloning and expression of the biodegradative threonine dehydratase gene (tdc) of Escherichia coli K12 [8].
• We have cloned the structural gene (tdcB) of biodegradative threonine deaminase from Escherichia coli W strain by utilizing the polymerase chain reaction [13].
• The physical and genetic structure of 37 kilobases of DNA encompassing the tdc region at 68.3 min of the Escherichia coli chromosome was determined by DNA sequence analysis and restriction mapping [14].

References