Effect of Mutations of Arginine 94 on Proton Pumping,Electron Transfer,and Superoxide Anion Generation in Cytochrome b of the bc1 Complex from Rhodobacter sphaeroides |
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Authors: | Yuan-Gang Qu Fei Zhou Linda Yu Chang-An Yu |
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Institution: | From the Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078 |
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Abstract: | Proton transfer involving internal water molecules that provide hydrogen bonds and facilitate proton diffusion has been identified in some membrane proteins. Arg-94 in cytochrome b of the Rhodobacter sphaeroides bc1 complex is fully conserved and is hydrogen-bonded to the heme propionate and a chain of water molecules. To further elucidate the role of Arg-94, we generated the mutations R94A, R94D, and R94N. The wild-type and mutant bc1 complexes were purified and then characterized. The results show that substitution of Arg-94 decreased electron transfer activity and proton pumping capability and increased O2˙̄ production, suggesting the importance of Arg-94 in the catalytic mechanism of the bc1 complex in R. sphaeroides. This also suggests that the transport of H+, O2, and O2˙̄ in the bc1 complex may occur by the same pathway. |
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Keywords: | Cytochrome b Mutant Protein Chemistry Proton Pumps Superoxide Ion bc1 Complex |
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