Proteins and glycoproteins of membranes from developing chick red cells

Membrane vesicles produced when chick erythroid cells are disrupted by nitrogen cavitation were isolated by centrifugation in a sucrose step gradient and purified on a linear sucrose gradient. Sodium dodecyl sulfate-polyacrylamide gel analysis of isolated membranes shows eight to ten proteins and four to five glycoproteins. Membranes must be prepared with protease inhibitors, otherwise an endogenous activity degrades high molecular weight polypeptide components. Red cells from several stages of development (5- and 17-day embryos and adult chickens) all appear to have the same major embrane proteins. However, primitive erythroid cells from 5-day embryos lack a Mr = 40,000 glycoprotein that is present in definitive erythrocytes from 17-day embryos and from adult chickens; erythrocytes from young chicks show a decrease in the amount of a glycoprotein of Mr = 50,000. Lactoperoxidase-catalyzed iodination of intact 5-day embryonic red cells detects three surface components which comigrate with the membrane glycoproteins on sodium dodecyl sulfate polyacrylamide gels.