Isolation of Photosystem II from the chlorophyll d-dominated cyanobacterium

Abstract

Acaryochloris marina is a unique prokaryote in which Chl d is a major pigment. The Chl a content of A. marina is variable, but it is always present. The primary electron donor of A. marina PS I was assigned to Chl d by Hu et al. In contrast, the primary electron donor of PS II is still under debate. Delayed fluorescence of PS II in the ns range was found only in Chl a region in intact cells. To identify the primary electron donor, we isolated the PS II particle from A. marina by a combination of two kinds of chromatography and sucrose density gradient centrifugation. The purified PS II preparation contained Chl d, Chl a, Pheo a, and α-carotene. Furthermore, PS II complexes retained electron transfer activity. Based on these observations, the assignment of the pigment and its role of PS II RC will be discussed.