title: Crystal structure of R-phycoerythrin from Polysiphonia urceolata at 2.8 A resolution.
abstract: The structure of R-phycoerythrin (R-PE) from Polysiphonia urceolata was determined at 2.8 A resolution. The crystals belong to space group R3 with unit cell dimensions of a = b = 189.8 A, c = 60.1 A. The subunit composition of R-PE is (alpha 2 beta 2)3 gamma. The three-dimensional structure of R-PE was solved by the multiple isomorphous replacement method. After several cycles of model building and refinement, the crystallographic R-factor of the final model is 18.0% with data from 10.0 to 2.8 A resolution. The four phycoerythrobilin chromophores alpha 84, alpha 140a, beta 84 and beta 155 in an (alpha beta) unit are each covalently bound to a cysteine residue through ring A. The phycourobilin chromophore is bound to cysteine beta 50 by ring A and bound to cysteine beta 61 by ring D. The ring A and ring D of phycourobilin deviate from the conjugate plane formed by ring B and ring C and the four rings form a boat-shaped structure. R-PE contains a 34 kDa gamma subunit that is assumed to lie in the central channel of the molecular disc (alpha 2 beta 2)3. The energy transfer and relationship between cysteine residues and chromophores are discussed.
authors.affiliation: National Laboratory of Biomacromolecules, Chinese Academy of Sciences, Beijing, China.
authors.forename: W R
authors.initials: WR
authors.lastname: Chang
authors.forename: T
authors.initials: T
authors.lastname: Jiang
authors.forename: Z L
authors.initials: ZL
authors.lastname: Wan
authors.forename: J P
authors.initials: JP
authors.lastname: Zhang
authors.forename: Z X
authors.initials: ZX
authors.lastname: Yang
authors.forename: D C
authors.initials: DC
authors.lastname: Liang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D045342:Light-Harvesting Protein Complexes; D008958:Models, Molecular; D010777:Photochemistry; D010788:Photosynthesis; D010799:Phycoerythrin / Q000737:chemistry / Q000648:ultrastructure*; D010940:Plant Proteins / Q000737:chemistry / Q000648:ultrastructure; D011487:Protein Conformation; D000461:Rhodophyta / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D010940:Plant Proteins; D010799:Phycoerythrin; D003545:Cysteine