Identification of the L-tartrate dehydratase genes (ttdA and ttdB) of Escherichia coli and evolutionary relationship with the class I fumarase genes.
The genes encoding an oxygen-labile stereospecific L-tartrate dehydratase (L-Ttd, EC 4.2.1.32) have been identified as the orfZ1 and orfZ2 genes located upstream of the rpsU-dnaG-rpoD operon at 67 min in the Escherichia coli linkage map. They were previously cloned and sequenced by M. Nesin and others (Gene 51, 149-161, 1987) and have now been independently cloned, partially resequenced, and designated as an operon (ttdAB) containing two translationally coupled genes. The enzyme behaves as a tetramer (M(r) 105,000) containing two pairs of non-identical subunits, TtdA (M(r) 32589) and TtdB (M(r) 22641), which otherwise resembles the homodimeric iron-sulphur-containing Class I fumarases of E. coli and Bacillus stearothermophilus. The amino acid sequences of the TtdA-TtdB subunits are colinearly related to a single fumarase subunit, indicating a common evolutionary ancestry. E. coli can use L-, D- and meso-tartrates as aerobic growth substrates and as reducible substrates for supporting anaerobic growth on glycerol. L-Ttd was induced during anaerobic growth on glycerol plus L- and meso-tartrates, and a stereospecific D-tartrate dehydratase was induced by all three stereoisomers under comparable conditions. No meso-tartrate dehydratase was detected, nor were any dehydratases detected after aerobic growth on tartrate minimal media suggesting that different catabolic routes operate under aerobic conditions.
Reaney
S K
SK
Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, UK.
Begg
C
C
Bungard
S J
SJ
Guest
J R
JR
D000595:Amino Acid Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005649:Fumarate Hydratase / Q000145:classification / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D005990:Glycerol / Q000378:metabolism; D006836:Hydro-Lyases / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism; D013379:Substrate Specificity; D013644:Tartrates / Q000378:metabolism
D013644:Tartrates; D006836:Hydro-Lyases; D005649:Fumarate Hydratase; C083087:L(+)-tartrate dehydratase; D005990:Glycerol