CELLULAR ARCHITECTURE II: PHOTOSYNTHETIC CORE COMPLEX

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 紫色细菌中的光合蛋白不仅执行复杂的能量转换过程，而且还负责将膜组织成具有明确形状的不同的细胞隔间。事实上，电子断层扫描和电子显微镜已经发现，紫色细菌中的光合蛋白聚集在膜中，形成不同形状和大小的独立光合作用单位，取决于物种和蛋白质的组成。在弯曲膜的光合蛋白中，球形红杆菌核心复合体是唯一被认为可以在细菌细胞中诱导圆柱形弯曲和建立管状小泡的复合体。然而，由于缺乏高分辨结构的核心复合体，使得研究其膜弯曲机理变得困难。本项目涉及一种非医用的光合作用生物体，因为膜形态发生对所有生物的细胞都很重要。以前，我们基于当时可用的二维电子显微镜投影图[2]构建了球形红杆菌核心复合体的基本全原子模型[1]，并表明核心复合体是一种二聚体结构，在周围的膜上略有弯曲并产生曲率。尽管这些模拟解释了核心复合体诱导膜弯曲的机制，但由于核心复合体结构的不确定性，观察到的曲率不足以再现已知大小的核心复合体管状囊泡。最近，三维电子显微镜地图出现，显示了高度弯曲的核心复合体[3]，并为进一步微调我们对核心复合体结构的理解提供了机会。用分子动力学柔性拟合法将早期的全原子模型与新的三维密度图[3]相结合，得到了改进的核心络合物模型[5，6]。复合体的大弯曲导致膜上的局部曲率很高，这与核心复合体管状囊泡的大小很好地吻合[5]。此外，模拟还展示了RC-LH1-PufX二聚体的局部曲率特性如何传播，形成观察到的球形红杆菌管状囊泡的远程组织[5]。生色团中光合蛋白的内禀曲率特性。生物群落。[2]钱平，C.N.Hunter，P.A.Bullough.球形红细菌核心Rc-LH1-PufX二聚体的8.5°A投影结构。J.Mol.《生物》，第349：948960,2005年。[3]钱平，P.A.布洛，C.N.亨特。膜弯曲复合体的三维重建：球形红杆菌的RC-LH1-PufX核心二聚体。J.Biol.《化学》，283：1400214011,2008年。[4]L.G.特拉布科，E.维拉，K.Mitra，J.Frank，K.Schulten。使用分子动力学灵活地将原子结构适配到电子显微镜图中。结构，2008年16：673683。[5]J.Hsin，J.Gumbart，L.G.Trabuo，E.Villa，P.Qian，C.N.Hunter，and K.Schulten.通过分子动力学柔性拟合研究蛋白质诱导的膜曲率.生物群落。J.，2009年。[6]M.K.Sener，J.Hsin，L.G.Trabuo，E.Villa，P.Qian，C.N.Hunter，和K.Schulten.球形红杆菌二聚体RC-LH1-PufX复合体的结构模型和激子性质.化学。体育，357：188197,2009年。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The photosynthetic proteins in purple bacteria not only carry out the intricate processof energy conversion, but are also responsible for organizing the membrane intodistinct cellular compartments with well-defined shapes. Indeed, electron tomographyand electron microscopy have discovered that the photosynthetic proteins inpurple bacteria aggregate in the membrane to form independent photosyntheticunits with different shapes and sizes depending on species and protein composition.Among the membrane-bending photosynthetic proteins, the Rhodobactersphaeroides core complex is the only one thought to induce cylindrical curvature andbuild tubular vesicles in bacterial cells. However, lack of high resolution structuresfor the core complex has rendered it difficult to investigate its membrane-bendingmechanism. This project deals with a non-medical photosynthetic organism becauseof the principle importance of membrane morphogenesis for the cells of allorganisms.Previously, we constructed a rudimentary all-atom model for the Rhodobactersphaeroides core complex [1] based on the then-available two-dimensional electronmicroscope projection map [2], and showed that the core complex, a dimeric construct,bends slightly and produces curvature in the surrounding membrane. Althoughthese simulations explain the mechanism of core complex-induced membranecurvature, the curvature observed was insufficient to reproduce the known size ofthe core complex tubular vesicles due to uncertainty of the core complex structure.Recently, a three-dimensional electron miscroscope map became available,displaying a highly-bent core complex [3] and provided an opportunity to furtherfine-tune our understanding of the core complex structure. Combining the earlierall-atom model with the new three-dimensional density map [3] using the moleculardynamics flexible fitting method [4], an improved core complex model was generated[5, 6]. The large bending of the complex induced a high local curvature in themembrane, which agreed well with the size of the core complex tubular vesicles [5].Furthermore, the simulations demonstrated how the local curvature properties ofthe RC-LH1-PufX dimer propagate to form the observed long-range organizationof the Rhodobacter sphaeroides tubular vesicles [5].BIBLIOGRAPHY[1] D. Chandler, J. Hsin, C. B. Harrison, J. Gumbart, and K. Schulten. Intrinsic curvatureproperties of photosynthetic proteins in chromatophores. Biophys. J., 95:28222836,2008.[2] P. Qian, C. N. Hunter, and P. A. Bullough. The 8.5 ¿A projection structure of the coreRC-LH1-PufX dimer of Rhodobacter sphaeroides. J. Mol. Biol., 349:948960, 2005.[3] P. Qian, P. A. Bullough, and C. N. Hunter. Three-dimensional reconstructionof a membrane-bending complex: The RC-LH1-PufX core dimer of Rhodobactersphaeroides. J. Biol. Chem., 283:1400214011, 2008.[4] L. G. Trabuco, E. Villa, K. Mitra, J. Frank, and K. Schulten. Flexible fitting ofatomic structures into electron microscopy maps using molecular dynamics. Structure,16:673683, 2008. PMCID: PMC2430731.[5] J. Hsin, J. Gumbart, L. G. Trabuco, E. Villa, P. Qian, C. N. Hunter, and K. Schulten.Protein-induced membrane curvature investigated through molecular dynamicsflexible fitting. Biophys. J., 2009. In press.[6] M. K. Sener, J. Hsin, L. G. Trabuco, E. Villa, P. Qian, C. N. Hunter, and K. Schulten.Structural model and excitonic properties of the dimeric RC-LH1-PufX complex fromRhodobacter sphaeroides. Chem. Phys., 357:188197, 2009.