Electron Transfer Reactions Involving Plastoquinone in Stacked and Unstacked Thylakoids

Abstract

Suspending thylakoids in a medium containing a low concentration (10–20 mM) of monovalent cations causes unstacking of the membranes. There is evidence that in this configuration all membrane proteins are randomly distributed in the lateral plane of the membrane (Andersson et al., 1980). There is also evidence that addition of salt to induce thylakoid stacking is associated with a redistribution of the photochemical reaction centres of the two photosysstems: the Photosystem I reaction centre thus partitions into the unappressed granal and stromal membranes, whereas the Photosystem II reaction centre predominantly partitions into the appressed granal membranes (Andersson, Anderson, 1980; Barber, 1980). This lateral heterogeneity of the two photosystems raises several questions as to the mechanisms of electron transfer between Photosystem II and Photosystem I. In the present study I have focused on electron transfer reactions involving the diffusible electron carrier plastoquinone.