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Solution structure of a biological bimolecular electron transfer complex: characterization of the photosynthetic reaction center‐cytochrome c 2 protein complex by small angle neutron scattering
Author(s) -
Tiede D. M.,
Littrell K.,
Marone P. A.,
Zhang R.,
Thiyagarajan P.
Publication year - 2000
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889800099891
Subject(s) - photosynthetic reaction centre , rhodobacter sphaeroides , chemistry , electron transfer , crystallography , kinetics , cytochrome , cytochrome c , neutron scattering , small angle neutron scattering , scattering , photochemistry , photosynthesis , organic chemistry , biochemistry , physics , quantum mechanics , optics , mitochondrion , enzyme
The structures of kinetically distinct electron transfer complexes formed between the photosynthetic reaction center from Rhodobacter sphaeroides R‐26, and a water‐soluble cytochrome c 2 were characterized using small angle neutron scattering, SANS. Reaction center‐cytochrome c 2 complexes, RC‐C, exhibiting predominately single exponential electron transfer kinetics were found to be 1:1 molar complexes, consistent with a low resolution, co‐crystal, x‐ray structure (Adir et al. , 1996), provided that the cofactor separation was adjusted to 14 ± 3 Å. Other RC‐C configurations are consistent with SANS data, but are distinguishable by cofactor separation. RC‐C preparations exhibiting more complex kinetics were found to have a particle volume markedly greater than that of a 1:1 complex. These results suggest that RC aggregation is associated with the variation in kinetics reported in the literature, and provide evidence that the model for the 1:1 complex in co‐crystals is relevant to the solution environment.