title: Ammonia-forming cytochrome c nitrite reductase from Sulfurospirillum deleyianum is a tetraheme protein: new aspects of the molecular composition and spectroscopic properties.
abstract: Ammonia-forming cytochrome c nitrite reductase from Sulfurospirillum deleyianum contains four covalently bound heme c groups/55 kDa subunit as determined by atomic absorption spectroscopy and the pyridine Fe(II)-hemochrome technique. Nitrite reductase was isolated from the membrane fraction as a monomer (M(r) 55 +/- 2 kDa) and as a heterooligomeric complex. Both the monomeric and the complex form of the enzyme exhibited a high specific activity, with up to 1050 mumol NO2-min-1 mg-1. The complex was built from four 55 kDa units and contained a 22 kDa c-type cytochrome which was absent in the monomeric form. EPR spectra of the complex displayed a prominent feature at g 4.83 (baseline crossing). This resonance, which was not observed in the spectra of the monomeric nitrite reductase, was assigned to the 22 kDa c-type cytochrome subunit. Identical results were obtained for the enzyme from Wolinella succinogenes which had been reinvestigated for comparison.
authors.affiliation: Fakultät für Biologie, Universität Konstanz, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Schumacher
authors.forename: U
authors.initials: U
authors.lastname: Hole
authors.forename: P M
authors.initials: PM
authors.lastname: Kroneck
mesh_terms: D001419:Bacteria / Q000201:enzymology*; D002850:Chromatography, Gel; D045263:Cytochromes a1; D003575:Cytochromes c1; D004578:Electron Spin Resonance Spectroscopy; D004591:Electrophoresis, Polyacrylamide Gel; D006418:Heme / Q000032:analysis*; D009565:Nitrate Reductases / Q000737:chemistry*
chemical_list: D006418:Heme; D045263:Cytochromes a1; D003575:Cytochromes c1; D009565:Nitrate Reductases; C054690:nitrate reductase (cytochrome)