Pigment–protein architecture in the light‐harvesting antenna complexes of purple bacteria: does the crystal structure reflect the native pigment–protein arrangement?

[摘要]

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.

[学科分类] 生物化学/生物物理

[关键词] Photosynthetic antenna complex;Circular aggregate;Crystal structure;Rhodobacter sphaeroides;Rhodopseudomonas acidophila;Rhodospirillum molischianum;LH1;LH2;core and peripheral light harvesting antenna complex of photosynthetic purple bacteria;LHC II;main light harvesting complex of higher plants;NIR;near-infrared spectral region;NLPF;non-linear polarization spectroscopy in the frequency domain;RC;reaction center;BChl a;Bacteriochlorophyll a;Rb.;Rhodobacter;Rps.;Rhodopseudomonas;Rsp.;Rhodospirillum