Article: article from journal or magazin.
Are the light-harvesting I complexes from Rhodospirillum rubrum arranged around the reaction centre in a square geometry?
Journal of molecular biology
Publication types: Journal Article ; Research Support, Non-U.S. Gov't - Publication Status: ppublish
The basic photosynthetic unit containing the reaction centre and the light-harvesting I complex (RC-LHI) of the purple non-sulphur bacterium Rhodospirillum rubrum was purified and reconstituted into two-dimensional (2D) membrane crystals. Transmission electron microscopy using conventional techniques and cryoelectron microscopy of the purified single particles and of 2D crystals yielded a projection of the RC-LHI complex at a resolution of at least 1.6 nm. In this projection the LHI ring appears to have a square symmetry and packs in a square crystal lattice. The square geometry of the LHI ring was observed also in images of single isolated particles of the RC-LHI complex. However, although the LHI units are packed identically within the crystal lattice, a new rotational analysis developed here showed that the reaction centres take up one of four possible orientations within the ring. This fourfold disorder supports our interpretation of a square ring symmetry and suggests that a hitherto undetected component may be present within the photosynthetic unit.
Bacterial Chromatophores, Bacterial Proteins, Cryoelectron Microscopy, Crystallization, Hydrogen-Ion Concentration, Light-Harvesting Protein Complexes, Microdialysis, Microscopy, Electron, Molecular Weight, Phospholipid Ethers, Photosynthetic Reaction Center Complex Proteins, Protein Conformation, Rhodospirillum rubrum, Solubility, Spectrum Analysis
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