36] Size and shape of membrane protein-detergent complexes: Hydrodynamic studies

Abstract

Publisher Summary Mild detergents, such as Triton X-100, are effective in solubilizing membrane proteins in largely native conformation. The mechanism of this solubilization is the substitution of bound detergent molecules for previously bound phospholipid/cholesterol molecules, and the result of the process is generally a lipid-free protein–detergent complex. By using sufficient quantities of pure preparations of membrane proteins, traditional hydrodynamic or other physical methods can be used to characterize the sizes and shapes of these complexes. However, when a membrane protein can only be obtained in limited amounts or as a mixture with other proteins, these methods are not applicable. This chapter describes a general method to obtain estimates of the hydrodynamic sizes and shapes of a variety of membrane protein–detergent complexes. These methods can provide information on proteins in crude mixtures if the identification of the species of interest by a biological activity (enzyme activity, ligand, or antibody binding) is possible.