SANS investigation of the photosynthetic machinery of Chloroflexus aurantiacus.
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.
Department of Biology, Washington University in St. Louis, Missouri, USA.
Kuo-Hsiang
KH
Tang
Volker S
VS
Urban
Jianzhong
J
Wen
Yueyong
Y
Xin
Robert E
RE
Blankenship
D000042:Absorption; D041861:Chloroflexus / Q000201:enzymology / Q000378:metabolism*; D004123:Dimethylamines / Q000378:metabolism; D004735:Energy Transfer; D005960:Glucosides / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D033363:Neutron Diffraction; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000201:enzymology / Q000378:metabolism; D053838:Scattering, Small Angle
D004123:Dimethylamines; D005960:Glucosides; D045342:Light-Harvesting Protein Complexes; D008055:Lipids; C018619:octyl-beta-D-glucoside; C014518:dodecyldimethylamine oxide