Studies on human tonsillar lymphocyte membranes. I. Isolation and characterization of a membraneous glycoprotein...

A microsomal fraction containing high amounts of plasma membrane has been isolated from human tonsillar lymphocytes. The subcellular fractions were characterized on the basis of their chemical composition and enzyme activities. A glycoprotein fraction solubilized by lithium-diiodo-salicylate (LIS) was purified by ion-exchange chromatography. The purified glycoprotein was analyzed by various methods and its carbohydrate content was determined. The glycoprotein contained large amounts of hexoses and sialic acid and this fraction represented 3--4% of the whole plasma membrane protein. The fraction was shown to consist of three individual proteins (4 X 10(4), 4.6 X 10(4) and 4.8 X 10(4) daltons) determined by SDS-polyacrylamide gel electrophoresis.