Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA.
Recently, structures of heterotrimeric G-protein subunits have been determined in isolation, in conjunction with each other, and in complex with their regulators. Along with biochemical information, these structures suggest how G-protein subunits are oriented relative to the membrane surface and relative to seven-transmembrane helix receptors. They also suggest mechanisms for receptor-catalyzed nucleotide exchange.