title: Refined three-dimensional structure of phycoerythrocyanin from the cyanobacterium Mastigocladus laminosus at 2.7 A.
abstract: The structure of the phycobiliprotein phycoerythrocyanin from the thermophilic cyanobacterium Mastigocladus laminosus has been determined at 2.7 A resolution by X-ray diffraction methods on the basis of the molecular model of C-phycocyanin from the same organism. Hexagonal phycoerythrocyanin crystals of space group P6(3) with cell constants a = b = 156.86 A, c = 40.39 A, alpha = beta = 90 degrees, gamma = 120 degrees are almost isomorphous to C-phycocyanin crystals. The crystal structure has been refined by energy-restrained crystallographic refinement and model building. The conventional crystallographic R-factor of the final model was 19.2% with data to 2.7 A resolution. In phycoerythrocyanin, the three (alpha beta)-subunits are arranged around a 3-fold symmetry axis, as in C-phycocyanin. The two structures are very similar. After superposition, the 162 C alpha atoms of the alpha-subunit have a mean difference of 0.71 A and the 171 C alpha atoms of the beta-subunit differ by 0.51 A. The stereochemistry of the chiral atoms in the phycobiliviolin chromophore A84 is C(31)-R, C(4)-S. The configuration of the chromophore is C(10)-Z, C(15)-Z and the conformation C(5)-anti, C(9)-syn and C(14)-anti like the phycocyanobilin chromophores in phycoerythrocyanin and C-phycocyanin.
authors.affiliation: Max-Planck Institut für Biochemie, Martinsried, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Duerring
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: W
authors.initials: W
authors.lastname: Bode
authors.forename: R
authors.initials: R
authors.lastname: Ruembeli
authors.forename: H
authors.initials: H
authors.lastname: Zuber
mesh_terms: D003196:Computer Graphics; D003461:Crystallography; D000458:Cyanobacteria; D004735:Energy Transfer; D008958:Models, Molecular; D052980:Phycobilins; D010798:Phycocyanin / Q000031:analogs & derivatives / Q000032:analysis / Q000648:ultrastructure*; D010860:Pigments, Biological; D011758:Pyrroles / Q000032:analysis; D013696:Temperature; D045725:Tetrapyrroles; D014961:X-Ray Diffraction
chemical_list: D052980:Phycobilins; D010860:Pigments, Biological; D011758:Pyrroles; D045725:Tetrapyrroles; C038397:phycoerythrocyanin; D010798:Phycocyanin; C063291:phycobiliviolin; C011069:phycocyanobilin