hide
Free keywords:
Sedimentation equilibrium; partial specific volume; molar mass; protein/ pigment/detergent micelles; light-harvesting complex B800/820
Abstract:
An adaptation of a procedure for the simultaneous determination of partial specific volumes and molar masses by sedimentation equilibrium experiments (Edelstein SJ, Schachman HK (1967) J Biol Chem 242: 306–311) to intrinsic membrane proteins in detergent solutions is described. The method requires (1) that the protein is available in at least two detergents the densities of which differ as much as possible, and (2) that the effective molar masses of the mixed protein/detergent micelles, M(1 − vρ 0), are determined under conditions of density matching. The method is applied to a pigment-containing membrane protein, the light-harvesting complex B800/820 (LH III) from Rhodospirillum molischianum, in solutions of three detergents. It is shown that the complex is the hexamer of the basic α/β/pigment unit.
