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Supramolecular organization of the photosynthetic apparatus of Rhodobacter sphaeroides
Author(s) -
Jungas Colette,
Ranck JeanLuc,
Rigaud JeanLouis,
Joliot Pierre,
Verméglio André
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.3.534
Subject(s) - rhodobacter sphaeroides , photosynthetic reaction centre , bacteriochlorophyll , purple bacteria , biology , cytochrome , rhodospirillaceae , membrane , crystallography , green sulfur bacteria , cytochrome c , supramolecular chemistry , light harvesting complex , photosynthesis , electron transport chain , cytochrome b , cytochrome b6f complex , photosystem ii , chemistry , photosystem i , botany , biochemistry , crystal structure , gene , mitochondrion , mitochondrial dna , enzyme
Native tubular membranes were purified from the purple non‐sulfur bacterium Rhodobacter sphaeroides . These tubular structures contain all the membrane components of the photosynthetic apparatus, in the relative ratio of one cytochrome bc 1 complex to two reaction centers, and ∼24 bacteriochlorophyll molecules per reaction center. Electron micrographs of negative‐stained membranes diffract up to 25 Å and allow the calculation of a projection map at 20 Å. The unit cell (a = 198 Å, b = 120 Å and γ = 103°) contains an elongated S‐shaped supercomplex presenting a pseudo‐2‐fold symmetry. Comparison with density maps of isolated reaction center and light‐harvesting complexes allowed interpretation of the projection map. Each supercomplex is composed of light‐harvesting 1 complexes that take the form of two C‐shaped structures of ∼112 Å in external diameter, facing each other on the open side and enclosing the two reaction centers. The remaining positive density is tentatively attributed to one cytochrome bc 1 complex. These features shed new light on the association of the reaction center and the light‐harvesting complexes. In particular, the organization of the light‐harvesting complexes in C‐shaped structures ensures an efficient exchange of ubihydroquinone/ubiquinone between the reaction center and the cytochrome bc 1 complex.