Chromophore content of C-phycoerythrin from various Cyanobacteria.

The molar extinction coefficient for phycoerythrobilin (l a) was calculated by two independent methods. It is different from that of the cleaved chromophore, phycobiliviolin (2). By unfolding with urea or tryptic digestion, the chromophore absorption of C-phycoerythrin (PE) was determined free of any protein influence. The chromophore content of PE from various Cyanobacteria was determined with these data to be either 5 or 6, depending on the organism. This corresponds to a chromophore distribution over phycoerythrin subunits alpha:beta of either 2:3 or 2:4. The phylogenetic significance of varying chromophore content is discussed.