Site-Directed NMR Studies on Membrane Proteins

Integral membrane proteins, traversing the membrane once or several times as α-helices, play crucial roles in maintaining various activities of cells such as transport of appropriate molecules into or out of the cell, catalysis of chemical reaction, and receiving and transducing chemical signals from the cell environment. Naturally, biological activity of such proteins may depend upon their conformations and dynamics regulated by specific lipid-protein and/or protein-protein interactions as structural determinants, as studied by analysis of 2D assembly of bacteriorhodopsin (bR) as a typical membrane protein [1]. bR is active as a proton pump and considered as a proto-type of a variety of G-protein coupled receptors, consisting of seven transmembrane α-helices.