title: Nitrate reductase from the magnetotactic bacterium Magnetospirillum magnetotacticum MS-1: purification and sequence analyses.
abstract: We purified the nitrate reductase from the soluble fraction of Magnetospirillum magnetotacticum MS-1. The enzyme was composed of 86- and 17-kDa subunits and contained molybdenum, non-heme iron, and heme c. These properties are very similar to those of the periplasmic nitrate reductase found in Paracoccus pantotrophus. The M. magnetotacticum nap locus was clustered in seven open reading frames, napFDAGHBC. The phylogenetic analyses of NapA, NapB, and NapC suggested a close relationship between M. magnetotacticum nap genes and Escherichia coli nap genes, which is not consistent with the 16S rDNA data. This is the first finding that the alpha subclass of Proteobacteria possesses a napFDAGHBC-type nap gene cluster. The nap gene cluster had putative fumarate and nitrate reduction regulatory protein (Fnr) and NarL protein binding sites. Furthermore, we investigated the effect of molybdate deficiency in medium on the total iron content of the magnetosome fraction and discussed the physiological function of nitrate reductase in relation to the magnetite synthesis in M. magnetotacticum.
authors.affiliation: Department of Biology, Faculty of Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Azuma
authors.initials: A
authors.lastname: Taoka
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yoshimatsu
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kanemori
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Fukumori
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003470:Culture Media; D052203:Ferrosoferric Oxide; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D008982:Molybdenum / Q000378:metabolism; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics* / Q000302:isolation & purification; D009876:Operon / Q000235:genetics; D010087:Oxides / Q000737:chemistry; D010802:Phylogeny; D012244:Rhodospirillaceae / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D017421:Sequence Analysis
chemical_list: D003470:Culture Media; D010087:Oxides; C044659:molybdate; D008982:Molybdenum; D007501:Iron; D009565:Nitrate Reductases; D050901:Nitrate Reductase; D052203:Ferrosoferric Oxide