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-terminal changes in the photosystem (PSII) II D1 protein were analysed by flash-induced oxygen evolution, chlorophyll a fluorescence decay kinetics and 77 K fluorescence emission spectra. The data presented here show 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 energy transfer between the phycobilisome and PSII and for stability of the PSII complex was demonstrated.