ENGINEERING OF N-TERMINAL THREONINES IN THE D1 PROTEIN IMPAIRS PHOTOSYSTEM-II ENERGY-TRANSFER IN SYNECHOCYSTIS-6803

Mutants of the cyanobacterium Synechocystis sp. PCC 6803 with N-termin al changes in the photosystem (PSII) II D1 protein were: analysed by f lash-induced oxygen evolution, chlorophyll a fluorescence decay kineti cs and 77 K fluorescence emission spectra. The data presented here sho w that mutations of the Thr-2, Thr-3 and Thr-4 in D1 do not influence the oxygen evolution. A perturbation on the acceptor side was observed and the importance of the N-terminal threonines for an efficient ener gy transfer between the phycobilisome and PSII and for stability of th e PSII complex was demonstrated. (C) 1998 Federation of European Bioch emical Societies.