PSI II reaction centers and energy transfer in a physphatidylglycerol deficient pgsa- mutant of Synecocystis PCC6803

Abstract

We analyzed energy transfer and electron transfer process in a Synecocystis PCC6803 mutant that has an inactivated pgsa gene, which functions as one of the terminal enzymes in the biosynthesis of a lipid phosphatidylglycerol (PG). 1) The depletion of PG from the medium increased the fractions of un-assembled PS II reaction center (RC) complex lacking CP43 or CP47. 2) The amount of PS I RC decreased. 3) The de novo synthesis of PS II proteins continued but the newly formed proteins were not incorporated into the PS II and PS I RC complexes. 4) We analyzed 77K fluorescence lifetime to know the energy transfer. The results indicated the decreased intensity of 694 nm band from CP47, the increases in the intensity and the lifetime of the 683 nm band, which was assigned to allophycocyanin fluorescence, while the lifetime of phycocyanin fluorescence was not affected indicating the proper assembly of phycobilisomes.