The isoelectric forms, quaternary structure and amino acid composition of peridinin-chlorophyll a-proteins from the symbiotic dinoflagellate Symbiodinium microadriaticum Freudenthal

Peridinin-chlorophyll a -protein (PCP) complexes isolated from three strains of the symbiotic dinoflagellate Symbiodinium microadriaticum Freudenthal have been found to occur in multiple isoelectric forms, but the pattern of isoelectric forms of PCP is characteristic of each strain. Analysis of PCP after growth of the algae from Tridacna maxima, Cassiopeia frondosa, and Rhodactis sancti-thomae at 22, 57 and 157 μmol m -2 s -1 demonstrated that the patterns remained unchanged. Determination of the native molecular mass, quaternary structure and amino acid composition of two isoelectric forms of PCP derived from algae from Anthopleura elegantissima and Rhodactis sancti-thomae showed similar native molecular masses and amino acid composition, but while PCP from the algae from A. elegantissima is dimeric, PCP from algae from R. sancti-thomae is monomeric. The potential use of PCP as a taxonomic tool in dinoflagellate systematics and the evolution of multiple forms of these pigment-protein complexes are discussed.