The properties of the protein of the plasma membrane of ox erythrocytes

Abstract

1. A method for the solubilisation of the protein of the ox erythrocyte ghost by butanol fractionation is described. The protein, as isolated, has a molecular weight of the order of 300 000, but a number of observations indicate that the preparation consists of particles of different sizes, possibly a series of aggregates of a smaller unit. In an ultracentifuge it separates into two fractions with sedimentation coefficients of 5 S and 10 S, each of which is itself heterogenous in size. 2. Electrophoresis, column chromatography and the effect of pH on solubility indicate that the protein is a sialoprotein, and, with the possible exception of some minor fractions amounting to about 10% of the total protein, no significant amount of protein free of sialic acid is detectable. Associated with the protein in the acqueous phase is a trace of lipid and about 8% by weight of carbohydrate. 3. The implications of these results to the organisation of the protein in the membrane are discussed.