Task 3

Supramolecular organization of membrane and membrane proteins

Image theme 3

The factors that control the formation of supercomplexes and their functional significance remain controversial: Crowding of a biological membrane with proteic complexes will force some organisation. This will in turn influence diffusion of substrates and signal by either (1) promoting channelling between complexes, (2) maintaining despite the crowding some pseudo random organisation of the membrane (3) promoting diffusion by creating substrate highways or (4) will act more indirectly by shaping the membrane as it has been proposed for the mitochondrial cristae.

Our understanding of the consequences of the ultra-structural organization of biological membranes on their function is still lacking or fragmented.  This project aims at filling this gap by combining structural studies that will determine the structure of defined pieces of biological membranes at high resolution, to functional studies. This will address the issue as to whether the function of these defined pieces sums up to the functions of their individual components.

Bioenergetic membranes are ideally suited for doing so. They are found in all living organisms and they obey common functional principles.  Yet, the topology of these membranes as well as the dynamics and organization of the supramolecular assemblies they embed differ. As an example, supercomplexes,  i.e. edifices that comprise within a single enzymatic unit several individual membrane complexes acting as individual links in the chain, have been found in mitochondria and chloroplast from a wide variety of organisms showing that some of them are sufficiently stable to be amenable to biochemical and structural studies, while others are more dynamical.  This raises the question of the overall architecture and functional role of the supercomplexes.

 

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