title: Molybdoenzyme biosynthesis in Escherichia coli: in vitro activation of purified nitrate reductase from a chlB mutant.
abstract: All molybdoenzyme activities are absent in chlB mutants because of their inability to synthesize molybdopterin guanine dinucleotide, which together with molybdate constitutes the molybdenum cofactor in Escherichia coli. The chlB mutants are able to synthesize molybdopterin. We have previously shown that the inactive nitrate reductase present in a chlB mutant can be activated in a process requiring protein FA and a heat-stable low-molecular-weight substance. We show here that purified nitrate reductase from the soluble fraction of a chlB mutant can be partially activated in a process that requires protein FA, GTP, and an additional protein termed factor X. It appears that the molybdopterin present in the nitrate reductase of a chlB mutant is converted to molybdopterin guanine dinucleotide during activation. The activation is absolutely dependent upon both protein FA and factor X. Factor X activity is present in chlA, chlB, chlE, and chlG mutants.
authors.affiliation: Laboratoire de Chimie Bactérienne, Centre National de la Recherche Scientifique, Marseille, France.
authors.forename: C L
authors.initials: CL
authors.lastname: Santini
authors.forename: C
authors.initials: C
authors.lastname: Iobbi-Nivol
authors.forename: C
authors.initials: C
authors.lastname: Romane
authors.forename: D H
authors.initials: DH
authors.lastname: Boxer
authors.forename: G
authors.initials: G
authors.lastname: Giordano
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002704:Chlorates / Q000494:pharmacology*; D003067:Coenzymes; D004352:Drug Resistance, Microbial / Q000235:genetics; D004789:Enzyme Activation; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D008667:Metalloproteins / Q000378:metabolism*; D008970:Molecular Weight; D000090006:Molybdenum Cofactors; D009154:Mutation; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics / Q000378:metabolism*; D011621:Pteridines / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D002704:Chlorates; D003067:Coenzymes; D006160:Guanosine Triphosphate; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D050901:Nitrate Reductase; D009565:Nitrate Reductases; D011621:Pteridines; C022261:molybdopterin