title: Cytochrome c4 can be involved in the photosynthetic electron transfer system in the purple bacterium Rubrivivax gelatinosus.
abstract: Three periplasmic electron carriers, HiPIP and two cytochromes c8 with low- and high-midpoint potentials, are present in the purple photosynthetic bacterium Rubrivivax gelatinosus. Comparison of the growth rates of mutants lacking one, two, or all three electron carrier proteins showed that HiPIP is the main electron donor to the photochemical reaction center and that high-potential cytochrome c8 plays a subsidiary role in the electron donation in photosynthetically growing cells. However, the triple deletion mutant was still capable of photosynthetic growth, indicating that another electron donor could be present. A new soluble cytochrome c, which can reduce the photooxidized reaction center in vitro, was purified. Based on amino acid sequence comparisons to known cytochromes, this cytochrome was identified as a diheme cytochrome c of the family of cytochromes c4. The quadruple mutant lacking this cytochrome and three other electron carriers showed about three times slower growth than the triple mutant under photosynthetic growth conditions. In conclusion, cytochrome c4 can function as a physiological electron carrier in the photosynthetic electron transport chain in R. gelatinosus.
authors.affiliation: Department of Biological Science, Tokyo Metropolitan University, Minamiohsawa 1-1, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Makito
authors.initials: M
authors.lastname: Ohmine
authors.forename: Katsumi
authors.initials: K
authors.lastname: Matsuura
authors.forename: Keizo
authors.initials: K
authors.lastname: Shimada
authors.forename: Jean
authors.initials: J
authors.lastname: Alric
authors.forename: André
authors.initials: A
authors.lastname: Verméglio
authors.forename: Kenji V P
authors.initials: KV
authors.lastname: Nagashima
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D020562:Betaproteobacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport / Q000235:genetics / Q000502:physiology*; D045222:Electron Transport Chain Complex Proteins / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D015345:Oligonucleotide Probes / Q000235:genetics; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D045222:Electron Transport Chain Complex Proteins; D007506:Iron-Sulfur Proteins; D015345:Oligonucleotide Probes; D045322:Photosynthetic Reaction Center Complex Proteins; C007943:high potential iron-sulfur protein; C034186:cytochrome C4; C017167:cytochrome C(551)