title: Isolation and characterization of soluble electron transfer proteins from Chromatium purpuratum.
abstract: Several soluble electron transfer proteins were isolated and characterized from the marine purple-sulfur bacterium Chromatium purpuratum. The C. purpuratum flavocytochrome c is similar in molecular mass (68 kDa) and isoelectric point (6.5) to flavocytochromes isolated from other phototrophs. Redox titrations of the flavocytochrome c hemes show two components with midpoint potential values of +15 and -120 mV, behavior similar to that observed with the flavocytochrome isolated from the thermophilic Chromatium tepidum. Moreover, N-terminal amino acid sequence analysis of both the flavin and the cytochrome subunit indicates substantial homology to the primary structure of the flavocytochrome c of Chromatium vinosum. In contrast, the C. purpuratum high-potential iron-sulfur protein (HiPIP) differs from those isolated from other photosynthetic bacteria in its relatively high midpoint potential (+390 mV) and the possibility that it exists as a dimer in solution. Two low molecular mass c-type cytochromes were also characterized. One appears to be a high-potential (+310 mV) c8-type cytochrome. Amino acid sequencing suggests that the second cytochrome may be a homologue of the low-potential cytochrome c-551, previously described in two species of Ectothiorhodospirillaceae.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles 90095, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Kerfeld
authors.forename: C
authors.initials: C
authors.lastname: Chan
authors.forename: M
authors.initials: M
authors.lastname: Hirasawa
authors.forename: S
authors.initials: S
authors.lastname: Kleis-SanFrancisco
authors.forename: T O
authors.initials: TO
authors.lastname: Yeates
authors.forename: D B
authors.initials: DB
authors.lastname: Knaff
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D002844:Chromatium / Q000254:growth & development / Q000378:metabolism*; D003574:Cytochrome c Group / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D004579:Electron Transport; D004591:Electrophoresis, Polyacrylamide Gel; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D007506:Iron-Sulfur Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C007943:high potential iron-sulfur protein; C017167:cytochrome C(551); D010088:Oxidoreductases; C064500:flavocytochrome c sulfide dehydrogenase