(448e) Structural and Functional Characterization of Photosynthetic Proteins in Marine Algae

The water-soluble peridinin-chlorophyll a-protein (PCP) and the membrane bound intrinsic light-harvesting complex (acpPC) are major light harvesting complexes in photosynthetic dinoflagellates, which are a group of marine algae. PCP contains the carotenoid peridinin and chlorophyll a, while acpPC contains an additional pigment chlorophyll c₂. In this study, we identified and characterized the PCP and acpPC proteins in Symbiodinium sp. CS-156. The apoPCP has a molecular mass of 32.7 kDa. Despite the heterogeneity of PCP gene tandem repeats, we identified a single form of PCP, which was sequenced by LC-MS/MS analysis of tryptic digested PCP.  Protein sequence comparison with the Amphidinium main form PCP (MFPCP) shows that the chl a and peridinin binding pockets are conserved in these two genera, which indicates the high degree of spectroscopic similarity and the same pigment stoichiometry; these hypotheses were confirmed by experiments. The spectroscopic characterization revealed that the peridinin-to-Chl a Q_y energy transfer efficiency is 95 % in this complex, which suggests that PCP may be promising for use in solar energy capture and eventual biofuel production in engineered devices.