title: Interaction with membranes of cytochrome c554 from Nitrosomonas europaea.
abstract: Two c-cytochromes extrinsically bound to the membranes of Nitrosomonas europaea have been identified. One is the tetraheme cytochrome c554, a protein previously described as soluble and periplasmic. Depending on the concentration of Fe and Cu in the growth medium, from 50 to 100% of the total cellular cytochrome c554 is membrane-associated. The cytochromes c554 found in the soluble or membrane fractions are identical in the spectroscopic, chromatographic, or primary structural properties examined. The interaction of cytochrome c554 with membranes is ionic in nature; it is disrupted by high concentrations of salt. Both membrane-derived and periplasmic forms of cytochrome c554 rebind tightly to membranes which have been washed free of the cytochrome. Cytochrome c554 binds to phospholipid vesicles, suggesting that phospholipids may play a role in the interaction of this cytochrome with the membrane. During the oxidation of NH2OH, the ability of the soluble hydroxylamine oxidoreductase (HAO) to transfer electrons to its natural electron acceptor, cytochrome c554, is substantially impaired when the latter is bound to phospholipid vesicles. The second c-cytochrome associated with membranes in N. europaea is identified as HAO based on its catalytic activity and the presence of a 464-nm ferrous absorption band. A small fraction of HAO is found to be membrane-bound and only in cells grown under low Fe/low Cu. This subpopulation of HAO can be released from the membranes without detergents.
authors.affiliation: Department of Genetics and Cell Biology, University of Minnesota, St. Paul 55108, USA.
authors.forename: H
authors.initials: H
authors.lastname: McTavish
authors.forename: D M
authors.initials: DM
authors.lastname: Arciero
authors.forename: A B
authors.initials: AB
authors.lastname: Hooper
mesh_terms: D001667:Binding, Competitive; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D003574:Cytochrome c Group / Q000032:analysis / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006418:Heme / Q000031:analogs & derivatives / Q000032:analysis; D008081:Liposomes / Q000378:metabolism; D009606:Nitrosomonas / Q000737:chemistry / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D011485:Protein Binding; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D003574:Cytochrome c Group; D008081:Liposomes; C083951:cytochrome c553; C031690:heme C; D006418:Heme; D012965:Sodium Chloride; C022302:cytochrome C-552; D010088:Oxidoreductases; C021401:hydroxylamine dehydrogenase