Center for Structural Molecular Biology, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
J Phys Chem B. 2009 Dec 24;113(51):16377-83. doi: 10.1021/jp905050b.
The structure of spinach light-harvesting complex II (LHC II), stabilized in a solution of the detergent n-octyl-beta-D-glucoside (BOG), was investigated by small-angle neutron scattering (SANS). Physicochemical characterization of the isolated complex indicated that it was pure (>95%) and also in its native trimeric state. SANS with contrast variation was used to investigate the properties of the protein-detergent complex at three different H(2)O/D(2)O contrast match points, enabling the scattering properties of the protein and detergent to be investigated independently. The topological shape of LHC II, determined using ab initio shape restoration methods from the SANS data at the contrast match point of BOG, was consistent with the X-ray crystallographic structure of LHC II (Liu et al. Nature 2004 428, 287-292). The interactions of the protein and detergent were investigated at the contrast match point for the protein and also in 100% D(2)O. The data suggested that BOG micelle structure was altered by its interaction with LHC II, but large aggregate structures were not formed. Indirect Fourier transform analysis of the LHC II/BOG scattering curves showed that the increase in the maximum dimension of the protein-detergent complex was consistent with the presence of a monolayer of detergent surrounding the protein. A model of the LHC II/BOG complex was generated to interpret the measurements made in 100% D(2)O. This model adequately reproduced the overall size of the LHC II/BOG complex, but demonstrated that the detergent does not have a highly regular shape that surrounds the hydrophobic periphery of LHC II. In addition to demonstrating that natively structured LHC II can be produced for functional characterization and for use in artificial solar energy applications, the analysis and modeling approaches described here can be used for characterizing detergent-associated alpha-helical transmembrane proteins.
菠菜捕光复合物 II（LHC II）的结构，在去污剂正辛基-β-D-吡喃葡萄糖苷（BOG）的溶液中稳定，通过小角中子散射（SANS）进行了研究。对分离复合物的理化特性进行了表征，表明其纯度大于 95%，并且仍处于其天然三聚体状态。使用对比变化的 SANS 研究了在三个不同的 H2O/D2O 对比匹配点下的蛋白质-去污剂复合物的性质，从而能够独立研究蛋白质和去污剂的散射特性。使用从头计算形状恢复方法从 SANS 数据在 BOG 的对比匹配点确定 LHC II 的拓扑形状，与 LHC II 的 X 射线晶体结构一致（Liu 等人，《自然》2004 年 428 卷，287-292 页）。在蛋白质的对比匹配点以及在 100%D2O 中研究了蛋白质和去污剂的相互作用。数据表明，BOG 胶束结构因与 LHC II 的相互作用而发生改变，但未形成大的聚集结构。LHC II/BOG 散射曲线的间接傅立叶变换分析表明，蛋白质-去污剂复合物的最大尺寸增加与存在围绕蛋白质的去污剂单层一致。生成了 LHC II/BOG 复合物的模型以解释在 100%D2O 中进行的测量。该模型充分再现了 LHC II/BOG 复合物的整体大小，但表明去污剂的形状不规则，无法完全包围 LHC II 的疏水区。除了证明可以生产天然结构的 LHC II 以进行功能表征和用于人工太阳能应用外，此处描述的分析和建模方法还可用于表征与去污剂相关的α-螺旋跨膜蛋白。
