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. 1992 Oct;138(10):2101-12. doi: 10.1099/00221287-138-10-2101.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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


  • Cytochromes
  • Escherichia coli Proteins
  • Quinones
  • Ubiquinone
  • S-Adenosylmethionine
  • Methyltransferases
  • UbiG protein, E coli

Associated data

  • GENBANK/M85087
  • GENBANK/M85088
  • GENBANK/M85089
  • GENBANK/M85090
  • GENBANK/M85091
  • GENBANK/M85092
  • GENBANK/M85093
  • GENBANK/M85094
  • GENBANK/M87509
  • GENBANK/M88253