Chromophore Content of C-Phycoerythrin from Various Cyanobacteria

Abstract

The molar extinction coefficient for phycoerythrobilin was calculated by 2 independent methods. It is different from that of the cleaved chromophore, phycobiliviolin. 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 [Pseudoanabaena catenata, Tolypothrix tenuis, Nostoc muscorum, Fremyella diplosiphon, Phormidium persicinum and P. autumnale] 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.