title: Purification and properties of ATP:GTP 3'-pyrophosphotransferase (guanosine pentaphosphate synthetase) from Streptomyces antibioticus.
abstract: Two forms of ATP:GTP 3'-pyrophosphotransferase (guanosine pentaphosphate synthetase) have been purified from Streptomyces antibioticus. The larger form has an M(r) of 88,000, while the M(r) of a smaller form is 47,000. Both synthetase forms are active in the formation of guanosine 5'-triphosphate, 3'-diphosphate in reaction mixtures containing methanol. Unlike the RelA protein from Escherichia coli, the synthetases from S. antibioticus do not use GDP efficiently as a substrate. Experiments using crude extracts of S. antibioticus mycelium and the 88,000-M(r) form of guanosine pentaphosphate synthetase strongly suggest that the 47,000-M(r) species is produced by proteolysis of the larger species. This conclusion is supported by the observation that antibody to either protein reacts with the other protein. Thus, the 88,000-M(r) species may be the catalytically relevant protein in vivo. Unlike the RelA protein, the 88,000-M(r) protein is not activated by ribosomes. Modest levels of guanosine pentaphosphate synthesis were observed in mycelial extracts derived from nine other actinomycetes.
authors.affiliation: Department of Biology, Emory University, Atlanta, Georgia 30322.
authors.forename: G H
authors.initials: GH
authors.lastname: Jones
mesh_terms: D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D007700:Kinetics; D008025:Ligases / Q000302:isolation & purification* / Q000378:metabolism*; D008970:Molecular Weight; D012270:Ribosomes / Q000201:enzymology; D013303:Streptomyces antibioticus / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D006153:Guanosine Diphosphate; D006165:Guanylyl Imidodiphosphate; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases