title: The periplasmic nitrate reductase in Shewanella: the resolution, distribution and functional implications of two NAP isoforms, NapEDABC and NapDAGHB.
abstract: In the bacterial periplasm, the reduction of nitrate to nitrite is catalysed by a periplasmic nitrate reductase (NAP) system, which is a species-dependent assembly of protein subunits encoded by the nap operon. The reduction of nitrate catalysed by NAP takes place in the 90 kDa NapA subunit, which contains a Mo-bis-molybdopterin guanine dinucleotide cofactor and one [4Fe-4S] iron-sulfur cluster. A review of the nap operons in the genomes of 19 strains of Shewanella shows that most genomes contain two nap operons. This is an unusual feature of this genus. The two NAP isoforms each comprise three isoform-specific subunits - NapA, a di-haem cytochrome NapB, and a maturation chaperone NapD - but have different membrane-intrinsic subunits, and have been named NAP-alpha (NapEDABC) and NAP-beta (NapDAGHB). Sixteen Shewanella genomes encode both NAP-alpha and NAP-beta. The genome of the vigorous denitrifier Shewanella denitrificans OS217 encodes only NAP-alpha and the genome of the respiratory nitrate ammonifier Shewanella oneidensis MR-1 encodes only NAP-beta. This raises the possibility that NAP-alpha and NAP-beta are associated with physiologically distinct processes in the environmentally adaptable genus Shewanella.
authors: Centre for Heavy Metals Research, School of Chemistry, University of Sydney, New South Wales 2006, Australia.
authors: Philippa J L
authors: PJL
authors: Simpson
authors: School of Biological Sciences, University of East Anglia, Norwich NR4 TJ7, UK.
authors: David J
authors: DJ
authors: Richardson
authors: School of Medical Sciences (Pharmacology) and Bosch Institute, University of Sydney, New South Wales 2006, Australia.|Centre for Heavy Metals Research, School of Chemistry, University of Sydney, New South Wales 2006, Australia.
authors: Rachel
authors: R
authors: Codd
mesh_terms: D000595:Amino Acid Sequence; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D009876:Operon; D019897:Periplasm / Q000201:enzymology; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011809:Quinones / Q000378:metabolism; D020592:Shewanella / Q000201:enzymology* / Q000235:genetics; D015533:Transcriptional Activation
chemical_list: D007527:Isoenzymes; D009566:Nitrates; D021122:Protein Subunits; D011809:Quinones; D050901:Nitrate Reductase