Reconstitution of bioenergetic proteins and the uses of proteoliposomes

Abstract

Abstract A variety of membrane proteins are involved in bioenergetic processes such as ATP synthesis, ATP hydrolysis coupled to ion and metabolite translocation, and redox reactions coupled to proton and sodium ion pumping. A study of their mechanism of action is often aided by purification and reconstitution into artificial bilayer systems, the most widely used of which is the liposome (1, 2). The advantage of reconstituted systems is that vectorial reactions of the protein can be recreated under defined conditions. The disadvantages are largely methodological. Problems can arise in the choice of reconstitution method, the lipid composition of the bilayer for optimum activity, and the yield and homogeneity of the final preparation. In addition, the properties of the vesicles themselves can impose constraints on the function of the protein. For example, the small vesicle size produced by some methods of preparation means that the electrogenic movement of just a few charged molecules can generate a significant membrane potential.