Purification and characterization of peridinin-chlorophyll a-proteins from the marine dinoflagellates Glenodinium sp. and Gonyaulax polyedra

Abstract

A peridinin-chlorophyll a-protein complex (PCP) was obtained in large quantity from the marine dinoflagellates, Glenodinium sp. and Gonyaulax polyedra. The chromoproteins have similar molecular weights, 35,500 for Glenodinium sp. and 34,500 for G. polyedra. The proteins from the PCP complex of Glenodinium sp. dissociated from the chromophore on treatment with 1% sodium dodecyl sulfate (SDS) at room temperature. The protein component was a single subunit with a molecular weight of 15,500. Proteins from the PCP complex of G. polyedra were composed of a single polypeptide with a molecular weight of about 32,000. Two peridinin-chlorophyll a-proteins from Glenodinium sp. accounted for 70% of the PCP complex and had isoelectric points of 7.4 and 7.3. The PCP complex from G. polyedra was dominated by a single chromoprotein with an isoelectric point of 7.2 Chromophore analysis indicated the presence of only peridinin and chlorophyll a in a molar ratio approaching 4:1. Other pigments characteristically found in dinoflagellates were absent. Fluorescence excitation spectra of purified PCP indicated an efficient energy transfer from peridinin to chlorophyll a, an observation that lends support to the reported role of peridinin as an accessory pigment in photosynthetic oxygen evolution. In several other brown colored dinoflagellates examined, PCP representtd less than 20% of the total peridinin. However, no PCP could be isolated from cultures of Amphidinium carterae (PY-1). This study provides further evidence that PCP is a normal component of most peridinin-containing dinoflagellates, and functions as a light-harvesting component of the dinoflagellate chloroplast. No fucoxanthin-containing analog of PCP was detected in the chrysophyte, Cricosphera carterae and the dinoflagellate Glenodinium foliaceum.