title: Crystal structure of R-phycocyanin and possible energy transfer pathways in the phycobilisome.
abstract: The crystal structure of R-phycocyanin from Polysiphonia urceolata (R-PC-PU) at 2.4 A is reported. The R-PC-PU crystal belongs to space group P4(3)2(1)2 with cell parameters a = 135.1 A, c = 210.0 A, and alpha = beta = gamma = 90 degrees. The structure was determined by molecular replacement. The crystallographic R-factor of the refined model is 0.189 (R(free) = 0.239). Comparison of the microenvironment of chromophore beta 155 in R-PC-PU and in C-PC from Fremyolla diphosiphon (C-PC-FD) reveals that their spectral differences may be caused by their different alpha 28 residues. In the R-PC-PU crystal structure, two (alpha beta)(3) trimers assemble face to face to form a hexamer, and two such hexamers assemble in two novel side-to-side arrangements. Possible models for the energy transfer from phycoerythrin to phycocyanin and from phycocyanin to allophycocyanin are proposed based on several phycobiliprotein crystal structures.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: T
authors.initials: T
authors.lastname: Jiang
authors.forename: J P
authors.initials: JP
authors.lastname: Zhang
authors.forename: W R
authors.initials: WR
authors.lastname: Chang
authors.forename: D C
authors.initials: DC
authors.lastname: Liang
mesh_terms: D020418:Algal Proteins / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D003461:Crystallography; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes; D008958:Models, Molecular; D008969:Molecular Sequence Data; D052980:Phycobilins; D045524:Phycobilisomes; D010798:Phycocyanin / Q000737:chemistry* / Q000378:metabolism*; D010799:Phycoerythrin / Q000737:chemistry / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D011758:Pyrroles / Q000737:chemistry / Q000378:metabolism; D000461:Rhodophyta / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D045725:Tetrapyrroles; D014961:X-Ray Diffraction
chemical_list: D020418:Algal Proteins; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D052980:Phycobilins; D045524:Phycobilisomes; D010940:Plant Proteins; D011758:Pyrroles; D045725:Tetrapyrroles; D010798:Phycocyanin; D010799:Phycoerythrin; C011070:phycoerythrobilin; C011069:phycocyanobilin