Cytochrome c4 Can Be Involved in the Photosynthetic Electron Transfer System in the Purple Bacterium Rubrivivax gelatinosus

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• 作者：Makito Ohmine ; Katsumi Matsuura ; Keizo Shimada ; Jean Alric ; Andr Vermglio ; Kenji V. P. Nagashima
• 刊名：Biochemistry
• 出版年：2009
• 出版时间：September 29, 2009
• 年：2009
• 卷：48
• 期：38
• 页码：9132-9139
• 全文大小：866K
• 年卷期：v.48,no.38(September 29, 2009)
• ISSN：1520-4995

文摘

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.