Electrophoretic Analysis of Polypeptides of Plasma Membranes from Bovine Pituitary Gland

Abstract

Purified plasma membranes from bovine hypophyseal tissue have been fractionated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis under various conditions of pH and acrylamide concentrations. The best separation of protein components is achieved at a concentration of 7.5% acrylamide and at pH 7.1. Under these conditions, the electrophoretic pattern consistently shows 36 protein bands ranging in molecular weights from 250 000 to 15 000. Only one broad band, having an apparent molecular weight of 150 000, stains for glycoproteins by the period acid – Schiff technique. After electrophoresis on a two-dimensional polyacrylamide gel system using disc gels containing urea and Triton X-100 in the first dimension and SDS in the second dimension, approximately 45 different protein components can be identified. Less than 12% of the membrane proteins are solubilized by washing the membranes with 1 M KCl or NH4Cl. Denaturating agents like urea and lithium 3,4-diiodosalycilate solubilize 55–60% of membrane components. Adenohypophyseal plasma membranes show an eleetrophoretic pattern completely different from that obtained with membranes isolated from the intermediate or posterior pituitary lobes.