SANS Investigation of the Photosynthetic Machinery of Chloroflexus aurantiacus

• Published in: Biophysical journal 2010-10, Vol.99 (8), p.2398-2407
• Main Authors: Tang, Kuo-Hsiang, Urban, Volker S., Wen, Jianzhong, Xin, Yueyong, Blankenship, Robert E.
• Format: Article
• Language: English
• Subjects: Absorption; Antennas; Bacteria; Biological Systems and Multicellular Dynamics; Biophysics; Chloroflexus - enzymology; Chloroflexus - metabolism; Chlorophyll; Dimethylamines - metabolism; Energy Transfer; Glucosides - metabolism; Light-Harvesting Protein Complexes - metabolism; Lipids; Lipids - chemistry; Neutron Diffraction; Neutron scattering; Photosynthesis; Reinforced concrete; Rhodobacter sphaeroides - enzymology; Rhodobacter sphaeroides - metabolism; Scattering; Scattering, Small Angle; Self assembly; Studies; Styrene acrylonitrile resins
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/j.bpj.2010.07.068

Green photosynthetic bacteria harvest light and perform photosynthesis in low-light environments, and contain specialized antenna complexes to adapt to this condition. We performed small-angle neutron scattering (SANS) studies to obtain structural information about the photosynthetic apparatus, including the peripheral light-harvesting chlorosome complex, the integral membrane light-harvesting B808-866 complex, and the reaction center (RC) in the thermophilic green phototrophic bacterium Chloroflexus aurantiacus. Using contrast variation in SANS measurements, we found that the B808-866 complex is wrapped around the RC in Cfx. aurantiacus, and the overall size and conformation of the B808-866 complex of Cfx. aurantiacus is roughly comparable to the LH1 antenna complex of the purple bacteria. A similar size of the isolated B808-866 complex was suggested by dynamic light scattering measurements, and a smaller size of the RC of Cfx. aurantiacus compared to the RC of the purple bacteria was observed. Further, our SANS measurements indicate that the chlorosome is a lipid body with a rod-like shape, and that the self-assembly of bacteriochlorophylls, the major component of the chlorosome, is lipid-like. Finally, two populations of chlorosome particles are suggested in our SANS measurements.