title: Structure of C-phycocyanin from Spirulina platensis at 2.2 A resolution: a novel monoclinic crystal form for phycobiliproteins in phycobilisomes.
abstract: The crystal structure of C-phycocyanin from the cyanobacterium S. platensis has been determined at 2.2 A resolution. The crystals belong to the monoclinic crystal form, which has not been previously reported for phycobiliprotein structures. The structure was solved using the molecular-replacement method with a final R value of 18.9% (R(free) = 23.7%) after model building and refinement. In the crystals used for the study, the C-phycocyanin hexamers formed by face-to-face association of two trimers are arranged in layers rather than in columns. Three different kinds of packing between adjacent hexamers in the layer were compared. The tight packing of two adjacent hexamers formed by four trimers in the asymmetric unit brings beta155 PCB chromophores close together, so it is possible that lateral energy transfer takes place through the beta155-beta155 route.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, People's Republic of China.
authors.forename: X Q
authors.initials: XQ
authors.lastname: Wang
authors.forename: L N
authors.initials: LN
authors.lastname: Li
authors.forename: W R
authors.initials: WR
authors.lastname: Chang
authors.forename: J P
authors.initials: JP
authors.lastname: Zhang
authors.forename: L L
authors.initials: LL
authors.lastname: Gui
authors.forename: B J
authors.initials: BJ
authors.lastname: Guo
authors.forename: D C
authors.initials: DC
authors.lastname: Liang
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D004734:Energy Metabolism; D045342:Light-Harvesting Protein Complexes; D008958:Models, Molecular; D008969:Molecular Sequence Data; D045524:Phycobilisomes; D010798:Phycocyanin / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D053545:Spirulina
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045524:Phycobilisomes; D010940:Plant Proteins; D010798:Phycocyanin