Pigment-protein architecture in the light-harvesting antenna complexes of purple bacteria: does the crystal structure reflect the native pigment-protein arrangement?
Structural analysis of crystallized peripheral (LH2) and core antenna complexes (LH1) of purple bacteria has revealed circular aggregates of high rotational symmetry (C8, C9 and C16, respectively). Quantum-chemical calculations indicate that in particular the waterwheel-like arrangements of pigments should show characteristic structure-sensitive spectroscopic behavior in the near infrared absorption region. Laser-spectroscopic data obtained with non-crystallized, isolated LH2 of Rhodospirillum molischianum are in line with a highly symmetric (C8) circular aggregate, but deviations have been found for LH2 of Rhodobacter sphaeroides and Rhodopseudomonas acidophila. For both the latter, C-shaped incomplete circular aggregates (as seen only recently in electron micrographs of crystallized LH1-reaction center complexes) may be a suitable preliminary model.
Leupold
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D
Max-Born-Institute for Non-linear Optics and Short Pulse Spectroscopy, Berlin, Germany. leupold@mbi-berlin.de
Voigt
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B
Beenken
W
W
Stiel
H
H
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D010860:Pigments, Biological / Q000737:chemistry*; D011487:Protein Conformation; D012241:Rhodopseudomonas / Q000737:chemistry*; D012246:Rhodospirillum / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared / Q000379:methods
C081521:B800-850 light-harvesting complex, bacteria; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010860:Pigments, Biological; C094744:light-harvesting complex 1, Rhodospirillum