Arabidopsis thylakoid domains proteome

The thylakoid membrane in land plants is organized into an appressed domain (grana), enriched in photosystem (PS) II, and a non-appressed domain (stroma lamellae) enriched in PSI. This ultrastructure ensures control over excitons spillover from PSII to PSI. The bulky machinery required for the repair and biogenesis of PSII and other proteins of the stacked, appressed domain is located in the non-appressed membranes. Thus, the connecting domain (CD) between grana and stroma lamellae, also known as the grana margins (GM), is the key player in both the structural and functional integrity of the photosynthetic machinery. To elucidate the properties and composition of the GM proteome, we have analyzed the different thylakoid domains isolated from membranes in native conformation as well as from thylakoids artificially unstacked to induce a homogeneous protein composition. We show that the composition of the CD is strictly distinct from that of the highly curved structures (the curvature) present at the periphery of grana discs, which are not physically connected to the stroma lamellae. Furthermore, a detailed map of the composition, distribution and interaction of the protein complexes involved in thylakoid membrane function is provided for the grana, CD, curvature and stroma lamellae domains.