SANS investigation of the photosynthetic machinery of Chloroflexus aurantiacus.

Kuo-Hsiang Tang, Volker S Urban, Jianzhong Wen, Yueyong Xin, Robert E Blankenship, Kuo-Hsiang Tang, Volker S. Urban, Jianzhong Wen, Yueyong Xin, Robert E. Blankenship

Index: Biophys. J. 99(8) , 2398-407, (2010)

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Abstract

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.Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.