Biophys J, August 2001, p. 1171-1179, Vol. 81, No. 2

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

National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China

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 P4₃2₁2 with cell parameters a = 135.1 Å, c = 210.0 Å, and  =  =  = 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 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 28 residues. In the R-PC-PU crystal structure, two ()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.

Biophys J, August 2001, p. 1171-1179, Vol. 81, No. 2
© 2001 by the Biophysical Society   0006-3495/01/08/1171/09  $2.00

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