Abstract

Phycocyanin is a phycobiliprotein involved in light harvesting and conduction of light to the reaction centers in cyanobacteria and red algae. The structure of C-phycocyanin from Gracilaria chilensis was solved by X-ray crystallography at 2.0 Å resolution in space group P2 1. An interaction model between two PC heterohexamers was built, followed by molecular dynamic refinement. The best model showed an inter-hexamer rotation of 23°. The coordinates of a PC heterohexamer (??) 6 and of the PC-PC complex were used to perform energy transfer calculations between chromophores pairs using the fluorescence resonance energy transfer approach (FRET). Two main intra PC ( I? 3 82 ? I? 1 84 ? I? 5 84 ? I? 6 82 and I? 3 153 ? I? 5 153) and two main inter PC ( I? 6 82 ? II? 3 82 and I? 5 153 ? II? 3 153) pathways were proposed based on the values of the energy transfer constants calculated for all the chromophore pairs in the hexamer and in the complex. © 2006 Elsevier B.V. All rights reserved.