PROTEIN CONFORMATION IN CELL MEMBRANE PREPARATIONS AS STUDIED BY OPTICAL ROTATORY DISPERSION AND CIRCULAR DICHROISM

Abstract

ORD [optical rotatory dispersion] and CD [circular dichroism] spectra of aqueous suspensions of membranes of human red blood cells and of Bacillus subtilis have been obtained and validated. The spectra show features which indicate that about one-quarter to one-third of the membrane protein is in a helical conformation, with the remainder most likely in the random-coil form. Certain unusual aspects of these protein spectra are observed with several different membrane systems, and suggest that a common protein structural feature is involved. The observations are interpreted in terms of a model of membrane structure which is consistent with recent information about the conformation of proteins and other macromolecules.