Lamellar Organization of Pigments in Chlorosomes, the Light Harvesting Complexes of Green Photosynthetic Bacteria
| Autor: | Pasi Laurinmäki, Michael C. Merckel, Ritva Serimaa, Teemu P. Ikonen, Roman Tuma, Jakub Pšenčík, Sarah J. Butcher |
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| Rok vydání: | 2004 |
| Předmět: |
Light-Harvesting Protein Complexes
Molecular Conformation Biophysics Chlorosome 02 engineering and technology Chlorobium 010402 general chemistry 01 natural sciences Light-harvesting complex chemistry.chemical_compound Lamellar structure Particle Size Photobiophysics biology Chemistry Cryoelectron Microscopy Chloroflexus aurantiacus Bacterial Chromatophores Pigments Biological 021001 nanoscience & nanotechnology biology.organism_classification 0104 chemical sciences Crystallography Chlorobium tepidum Bacteriochlorophyll Photosynthetic bacteria 0210 nano-technology |
| Zdroj: | Biophysical Journal. 87:1165-1172 |
| ISSN: | 0006-3495 |
| DOI: | 10.1529/biophysj.104.040956 |
| Popis: | Chlorosomes of green photosynthetic bacteria constitute the most efficient light harvesting complexes found in nature. In addition, the chlorosome is the only known photosynthetic system where the majority of pigments (BChl) is not organized in pigment-protein complexes but instead is assembled into aggregates. Because of the unusual organization, the chlorosome structure has not been resolved and only models, in which BChl pigments were organized into large rods, were proposed on the basis of freeze-fracture electron microscopy and spectroscopic constraints. We have obtained the first high-resolution images of chlorosomes from the green sulfur bacterium Chlorobium tepidum by cryoelectron microscopy. Cryoelectron microscopy images revealed dense striations approximately 20 A apart. X-ray scattering from chlorosomes exhibited a feature with the same approximately 20 A spacing. No evidence for the rod models was obtained. The observed spacing and tilt-series cryoelectron microscopy projections are compatible with a lamellar model, in which BChl molecules aggregate into semicrystalline lateral arrays. The diffraction data further indicate that arrays are built from BChl dimers. The arrays form undulating lamellae, which, in turn, are held together by interdigitated esterifying alcohol tails, carotenoids, and lipids. The lamellar model is consistent with earlier spectroscopic data and provides insight into chlorosome self-assembly. |
| Databáze: | OpenAIRE |
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