title: Determination of the topological shape of integral membrane protein light-harvesting complex LH2 from photosynthetic bacteria in the detergent solution by small-angle X-ray scattering.
abstract: The topological shape of the integral membrane protein light-harvesting complex LH2 from photosynthetic bacteria Rhodobacter spheroides 2.4.1 in detergent solution has been determined from synchrotron small-angle X-ray scattering data using direct curve-fitting by the ellipsoid, ab initio shape determination methods of simulated annealing algorithm and multipole expansion, respectively. The results indicate that the LH2 protein in aqueous solution is encapsulated by a monolayered detergent shell. The detergent-stabilized structure has the shape of an oblate plate, with a thickness of 40 A, a long axis of 110 A, and a short axis of 85 A. After correction for the detergent shell, the shape of the LH2 core is also an oblate plate with a height of 40 A, a long axis of 80 A, and a short axis of 55 A. In contrast to the cylindrical crystal structure with a height of 40 A and a diameter of 68 A, the molecular shape of the LH2 complex in detergent solution clearly deviates from the ringlike crystal structure, with an eccentricity found to be 0.59-consistent with the result of single molecular spectroscopy study of the isolated single LH2 molecules.
authors.affiliation: Laboratory of Soft Matter Physics, Institute of Physics, and Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xinguo
authors.initials: X
authors.lastname: Hong
authors.forename: Yu-Xiang
authors.initials: YX
authors.lastname: Weng
authors.forename: Ming
authors.initials: M
authors.lastname: Li
mesh_terms: D000465:Algorithms; D003902:Detergents / Q000737:chemistry*; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011487:Protein Conformation; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D012996:Solutions; D014867:Water; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D003902:Detergents; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045332:Photosystem II Protein Complex; D012996:Solutions; D014867:Water