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

Jiang, J., Washington University
Lo, C. S., Washington University in St. Louis
Blankenship, R., Washington University in St. Louis
Zhang, H., Washington University in St. Louis

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 Qy 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.