Cloning of a guanosine-inosine kinase gene of Escherichia coli and characterization of the purified gene product

J Bacteriol. 1995 Sep;177(17):4921-6. doi: 10.1128/jb.177.17.4921-4926.1995.

Abstract

We attempted to clone an inosine kinase gene of Escherichia coli. A mutant strain which grows slowly with inosine as the sole purine source was used as a host for cloning. A cloned 2.8-kbp DNA fragment can accelerate the growth of the mutant with inosine. The fragment was sequenced, and one protein of 434 amino acids long was found. This protein was overexpressed. The overexpressed protein was purified and characterized. The enzyme had both inosine and guanosine kinase activity. The Vmaxs for guanosine and inosine were 2.9 and 4.9 mumol/min/mg of protein, respectively. The Kms for guanosine and inosine were 6.1 microM and 2.1 mM, respectively. This enzyme accepted ATP and dATP as a phosphate donor but not p-nitrophenyl phosphate. These results show clearly that this enzyme is not a phosphotransferase but a guanosine kinase having low (Vmax/Km) activity with inosine. The sequence of the gene we have cloned is almost identical to that of the gsk gene (K.W. Harlow, P. Nygaard, and B. Hove-Jensen, J. Bacteriol. 177:2236-2240, 1995).

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cloning, Molecular
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Genes, Bacterial / genetics*
  • Hydrolysis
  • Inosine / metabolism
  • Molecular Sequence Data
  • Phosphotransferases (Alcohol Group Acceptor) / biosynthesis
  • Phosphotransferases (Alcohol Group Acceptor) / genetics*
  • Phosphotransferases (Alcohol Group Acceptor) / isolation & purification
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • Recombinant Proteins / biosynthesis
  • Restriction Mapping
  • Sequence Analysis, DNA
  • Sequence Homology, Amino Acid
  • Substrate Specificity

Substances

  • Recombinant Proteins
  • Inosine
  • Phosphotransferases (Alcohol Group Acceptor)
  • inosine kinase

Associated data

  • GENBANK/D00798