Blue-green algal proteins: assembly forms of C-phycocyanin from Synechococcus sp.

Aggregation states of C-phycocyanin isolated from Synechococcus sp. strain 6301 ( Anacystis nidulans ) were examined both by spectrophotometric and electron microscopic methods. The electron microscope observations support previous results which showed that the separated α and β chains of the protomer can be recombined in vitro to form a reversible aggregate (hexamer) composed of 6 copies of each chain. This aggregate has the same disc shape as native phycocyanin, and the assembly process can be followed in solution by distinctive changes in circular dichroism properties. A new observation was the occurrence of higher assembly forms (short rods and ordered bundles) probably related to the structure of the intact phycobilisome. However, conditions were not found which allow assembly of these structural forms in vitro from highly purified phycocyanin alone.