Distribution of intrinsic and extrinsic subunits of the PS II protein complex between appressed and non-appressed regions of the thylakoid membrane: an immunocytochemical study

AbstractThe distribution of photosystem (PS) II centers between appressed and non-appressed domains of the thylakoid membranes has been investigated, using immunogold labeling, in C. reinhardtii and in spinach. We have used antibodies directed against the two main intrinsic subunits of the PS II center and against two extrinsic subunits of the O2-evolving site. 90% of the two intrinsic PS II antigens are located in the appressed membranes, in a density 3–3.5-fold higher than in the non-appressed regions. The same distribution is observed for the two extrinsic antigens. This result suggests that the O2-evolving system is associated with the PS II center, both in appressed and in non-appressed regions of the thylakoid membrane