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Scientific article
English

Two-dimensional crystallization of the light-harvesting I - reaction centre photounit from Rhodospirillum rubrum

Published inJournal of Molecular Biology, vol. 265, no. 2, p. 107-111
Publication date1997-01
Abstract

A stoichiometric unit of the light-harvesting complex I and the reaction centre (LHI-RC complex) has been isolated from a carotenoid-less mutant of the purple non-sulphur bacterium Rhodospirillum rubrum by mild solubilization of photosynthetic membranes with the phospholipid detergent diheptylphosphatidylcholine. Dialysis of the isolated LHI-RC complexes in the presence of added dioleoyl-sn-phosphatidylcholine produced ordered two-dimensional crystals. Digital image processing revealed that the LHI-RC are packed together in a square lattice (a = b = 16.3 nm). The dimensions of the LHI ring are essentially identical with those determined from two-dimensional (2D) crystals of purified carotenoid-containing light-harvesting I complexes after analysis by cryo-electron microscopic techniques or from negatively stained 2D crystals of purified LHI complexes from a carotenoid-less mutant. Each LHI ring of the LHI-RC complex contains a central diffuse stain-excluding region, which is assigned to the reaction centre. The analysis of the LHI-RC 2D crystals strongly suggests that the geometry and subunit stoichiometry of the LHI ring is unaffected by the presence of a reaction centre that can probably assume various orientations within the ring.

eng
Keywords
  • Light-harvesting complex
  • 2D crystallization
  • Reaction centre
  • Rhodospirillum rubrum
  • Image processing
  • Electron microscopy
Citation (ISO format)
WALZ, Thomas, GHOSH, Robin. Two-dimensional crystallization of the light-harvesting I - reaction centre photounit from <i>Rhodospirillum rubrum</i>. In: Journal of Molecular Biology, 1997, vol. 265, n° 2, p. 107–111. doi: 10.1006/jmbi.1996.0714
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ISSN of the journal0022-2836
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