Dynamics of bioenergetic microcompartments.

The vast majority of life on earth is dependent on harvesting electrochemical potentials over membranes for the synthesis of ATP. Generation of membrane potential often relies on electron transport through membrane protein complexes, which vary among the bioenergetic membranes found in living organisms. In order to maximize the efficient harvesting of the electrochemical potential, energy loss must be minimized, and this is achieved partly by restricting certain events to specific microcompartments, on bioenergetic membranes. In this review we will describe the characteristics of the energy-converting supramolecular structures involved in oxidative phosphorylation in mitochondria and bacteria, and photophosphorylation. Efficient function of electron transfer pathways requires regulation of electron flow, and we will also discuss how this is partly achieved through dynamic re-compartmentation of the membrane complexes into different supercomplexes. In addition to supercomplexes, the supramolecular structure of the membrane, and in particular the role of water layers on the surface of the membrane in the prevention of wasteful proton escape (and therefore energy loss), is discussed in detail. In summary, the restriction of energetic processes to specific microcompartments on bioenergetic membranes minimizes energy loss, and dynamic rearrangement of these structures allows for regulation.