Crystal Structure of R-Phycocyanin and Possible Energy Transfer Pathways in the Phycobilisome

• Published in: Biophysical journal 2001-08, Vol.81 (2), p.1171-1179
• Main Authors: Jiang, Tao, Zhang, Ji-ping, Chang, Wen-rui, Liang, Dong-cai
• Format: Article
• Language: English
• Subjects: Algal Proteins - chemistry; Algal Proteins - metabolism; Amino Acid Sequence; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Biochemistry; Biology; Cells; Crystallography; Energy; Energy Transfer; Light-Harvesting Protein Complexes; Models, Molecular; Molecular Sequence Data; Phycobilins; Phycobilisomes; Phycocyanin - chemistry; Phycocyanin - metabolism; Phycoerythrin - chemistry; Phycoerythrin - metabolism; Physics; Plant Proteins - chemistry; Plant Proteins - metabolism; Protein Conformation; Proteins; Pyrroles - chemistry; Pyrroles - metabolism; Rhodophyta - chemistry; Sequence Homology, Amino Acid; Static Electricity; Tetrapyrroles; X-Ray Diffraction
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/S0006-3495(01)75774-8

The crystal structure of R-phycocyanin from Polysiphonia urceolata (R-PC-PU) at 2.4 Å is reported. The R-PC-PU crystal belongs to space group P4 32 12 with cell parameters a = 135.1 Å, c = 210.0 Å, and α = β = γ = 90°. 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 β155 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 α28 residues. In the R-PC-PU crystal structure, two ( αβ) 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.