Ammonia-Forming Cytochrome c Nitrite Reductase from Sulfurospirillum deleyianum Is a Tetraheme Protein: New Aspects of the Molecular Composition and Spectroscopic Properties

• Published in: Biochemical and biophysical research communications Vol. 205; no. 1; pp. 911 - 916
• Main Authors: Schumacher, W., Hole, U., Kroneck, M.H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.11.1994
• Subjects: Bacteria - enzymology; Chromatography, Gel; Cytochromes a1; Cytochromes c1; Electron Spin Resonance Spectroscopy; Electrophoresis, Polyacrylamide Gel; Heme - analysis; Nitrate Reductases - chemistry
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1994.2751

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 (Mr 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 μmol 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.