Department of Biology, Washington University in St. Louis, Missouri, USA.
Biophys J. 2010 Oct 20;99(8):2398-407. 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.
绿光合细菌在低光环境中收集光并进行光合作用，并含有专门的天线复合物以适应这种情况。我们进行了小角中子散射（SANS）研究，以获取光合作用器的结构信息，包括外围的光收集叶绿素体复合物、整体膜光收集 B808-866 复合物和嗜热绿光合细菌 Chloroflexus aurantiacus 中的反应中心（RC）。通过 SANS 测量中的对比变化，我们发现 B808-866 复合物在 Cfx. aurantiacus 中围绕 RC 缠绕，并且 Cfx. aurantiacus 的 B808-866 复合物的整体大小和构象大致与紫色细菌的 LH1 天线复合物相当。动态光散射测量表明分离的 B808-866 复合物具有相似的大小，并且观察到 Cfx. aurantiacus 的 RC 比紫色细菌的 RC 小。此外，我们的 SANS 测量表明，叶绿素体是一种具有棒状形状的脂质体，并且叶绿素体的主要成分细菌叶绿素的自组装是类脂样的。最后，我们的 SANS 测量表明存在两种叶绿素体颗粒群体。
