title: Crystal structure of a light-harvesting protein C-phycocyanin from Spirulina platensis.
abstract: The crystal structure of C-phycocyanin, a light-harvesting phycobiliprotein from cyanobacteria (blue-green algae) Spirulina platensis has been solved by molecular replacement technique. The crystals belong to space group P2(1) with cell parameters a = 107.20, b = 115.40, c = 183.04 A; beta = 90.2 degrees. The structure has been refined to a crystallographic R factor of 19.2% (R(free) = 23.9%) using the X-ray diffraction data extending up to 2.2 A resolution. The asymmetric unit of the crystal cell consists of two (alphabeta)6-hexamers, each hexamer being the functional unit in the native antenna rod of cyanobacteria. The molecular structure resembles that of other reported C-phycocyanins. However, the unique form of aggregation of two (alphabeta)6-hexamers in the crystal asymmetric unit, suggests additional pathways of energy transfer in lateral direction between the adjacent hexamers involving beta155 phycocyanobilin chromophores.
authors.affiliation: Department of Physics, Indian Institute of Science, Bangalore, 560 012, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Padyana
authors.forename: V B
authors.initials: VB
authors.lastname: Bhat
authors.forename: K M
authors.initials: KM
authors.lastname: Madyastha
authors.forename: K R
authors.initials: KR
authors.lastname: Rajashankar
authors.forename: S
authors.initials: S
authors.lastname: Ramakumar
mesh_terms: D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000737:chemistry*; D008958:Models, Molecular; D010798:Phycocyanin / Q000737:chemistry*; D017433:Protein Structure, Secondary; D021122:Protein Subunits
chemical_list: D021122:Protein Subunits; D010798:Phycocyanin