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.
Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, UK.
S K
SK
Reaney
C
C
Begg
S J
SJ
Bungard
J R
JR
Guest
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