One century of protein crystallography: the phycobiliproteins.

The physical principles that underlay the rapid and efficient energy transfer from the light absorbing phycobilisomes to the reaction centre are conceivable from the knowledge of the exact three-dimensional structure of the phycobiliproteins and chromophores that are involved. The structure of the components and their assembly in the phycobilisomes could be determined by the structure analysis of X-ray data derived from phycobiliprotein crystals. Reports about these very aesthetic and brilliantly colored crystals have been published for more than a hundred years but it was only in the last decade that the structures of the different members of the phycobiliprotein family were solved for the first time at atomic resolution--all of them in Martinsried at the Max-Planck-Institut für Biochemie. Despite the appearance of common structural principles the most important finding was that very subtle modifications in the structure and environment of the chromophores are sufficient to establish a highly specific light harvesting system in which the phycobiliproteins function with great cooperativity and efficiency.