title: 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.
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 bc(1) 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 bc(1) complexes were purified and then characterized. The results show that substitution of Arg-94 decreased electron transfer activity and proton pumping capability and increased O(2)(.) production, suggesting the importance of Arg-94 in the catalytic mechanism of the bc(1) complex in R. sphaeroides. This also suggests that the transport of H(+), O(2), and O(2)(.) in the bc(1) complex may occur by the same pathway.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078, USA. yuangangqu@yahoo.com
authors.forename: Yuan-Gang
authors.initials: YG
authors.lastname: Qu
authors.forename: Fei
authors.initials: F
authors.lastname: Zhou
authors.forename: Linda
authors.initials: L
authors.lastname: Yu
authors.forename: Chang-An
authors.initials: CA
authors.lastname: Yu
mesh_terms: D001120:Arginine / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D014450:Electron Transport Complex III / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010788:Photosynthesis; D016133:Polymerase Chain Reaction; D017494:Proton Pumps / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000201:enzymology* / Q000502:physiology
chemical_list: D017931:DNA Primers; D017494:Proton Pumps; D001120:Arginine; D014450:Electron Transport Complex III