Guanylate kinase of Escherichia coli K-12.
We have identified the gene gmk, in the same operon as rpoZ, spoT, and recG at about 82 minutes on the Escherichia coli chromosome. The gmk (GMP kinase) gene encodes a peptide of 23,592 Da, possessing extensive similarity to the amino acid sequence of guanylate kinase from yeast. To confirm that gmk truly encodes guanylate kinase and to explore some of its enzymatic features, we have overproduced the product of gmk and purified it to homogeneity. Unlike guanylate kinases purified from eukaryotic sources, E. coli guanylate kinase is multimeric, and ionic conditions dictate its protomeric state; under low ionic conditions it appears to be a tetramer while under high ionic conditions it is a dimer. Kinetic analysis reveals that guanylate kinase, again, unlike eukaryotic guanylate kinases, binds GMP cooperatively and that the observed cooperatively changes with ionic strength. These results indicate that, despite extensive sequence similarity to its eukaryotic counterparts, E. coli guanylate kinase is structurally and enzymatically different.
Gentry
D
D
Section on Molecular Regulation, National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
Bengra
C
C
Ikehara
K
K
Cashel
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D005798:Genes, Bacterial; D005809:Genes, Regulator; D006157:Guanosine Monophosphate / Q000378:metabolism; D051528:Guanylate Kinases; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009703:Nucleoside-Phosphate Kinase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D009838:Oligodeoxyribonucleotides; D009876:Operon; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D006157:Guanosine Monophosphate; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases