PMID:1479344
| Citation |
Wu, G, Williams, HD, Zamanian, M, Gibson, F and Poole, RK (1992) Isolation and characterization of Escherichia coli mutants affected in aerobic respiration: the cloning and nucleotide sequence of ubiG. Identification of an S-adenosylmethionine-binding motif in protein, RNA, and small-molecule methyltransferases. J. Gen. Microbiol. 138:2101-12 |
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| Abstract |
We report the isolation and characterization of a mutant of Escherichia coli unable to grow aerobically on non-fermentable substrates, except for very slow growth on glycerol. The mutant contains cytochrome oxidases o and d, and grows anaerobically with alternative electron acceptors. Oxygen consumption rates of cell-free extracts were low relative to activities in an isogenic control strain, but were restored in vitro by adding ubiquinone-1 to cell-free extracts. Transformation with a cloned 2.8 kb ClaI-EcoRV fragment of chromosomal DNA restored the ability of this mutant (AN2571) to grow on succinate and also restored cellular quinone levels in this strain. The plasmid also complemented a previously isolated ubiG mutant (AN151) for aerobic growth on succinate. The nucleotide sequence revealed a 0.7 kb portion of gyrA. Unidirectional nested deletions from this fragment and complementation analysis identified an open reading frame encoding a protein with a predicted molecular mass of 26.5 kDa. This gene (ubiG) encodes the enzyme 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone methyltransferase, which catalyses the terminal step in the biosynthesis of ubiquinone. The open reading frame is preceded by a putative Shine-Dalgarno sequence and followed by three palindromic unit sequences. Comparison of the inferred amino acid sequence of UbiG with the sequence of other S-adenosylmethionine (AdoMet)-dependent methyltransferases reveals a highly conserved AdoMet-binding region. The cloned 2.8 kb fragment also contains a sequence encoding the C-terminus of a protein with 42-44% identity to fungal acetyl-CoA synthetases. |
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| Keywords |
Aerobiosis; Amino Acid Sequence; Base Sequence; Cloning, Molecular; Cytochromes/analysis; DNA Mutational Analysis; Escherichia coli/enzymology; Escherichia coli/genetics; Escherichia coli Proteins; Genetic Complementation Test; Methyltransferases/genetics; Molecular Sequence Data; Mutation; Nucleic Acid Conformation; Oxygen Consumption/genetics; Quinones/analysis; S-Adenosylmethionine/metabolism; Sequence Homology, Amino Acid; Ubiquinone/biosynthesis |
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