Membrane Glycopeptides from Subcellular Fractions of Control and Virus-transformed Cells

Abstract

The glycopeptides from various subcellular fractions isolated from control, BHK₂₁/C₁₃, and virus-transformed C₁₃/ B₄ baby hamster kidney cells have been compared by chromatography on columns of Sephadex G-50 in order to determine (a) whether changes in cell surface glycoproteins previously shown to occur upon viral transformation are also found in the glycoproteins of membranes associated with other subcellular membrane fractions and (b) whether the glycopeptides associated with the subcellular fractions were similar to those found on the surface membrane. Cells were grown in the presence of d-[¹⁴C]- or [³H]glucosamine or l-[¹⁴C]- or [³H]fucose. Fractions to be compared were mixed and digested with pronase, and the glycopeptides were fractionated by gel filtration. These studies showed that the alterations accompanying transformation seen in the surface membrane glycopeptides were also found in other subcellular fractions. These alterations consist of as marked increase in the amount of higher molecular weight material in the transformed cell. Neuraminidase treatment of this material diminishes or eliminates the difference between the normal and malignant patterns. The relative distribution of glycopeptides in the mitochondrial, nuclear, and rough endoplasmic reticular fractions differed in some respects from that of the surface membrane. Glycopeptides associated with the subcellular fractions were not due to contamination by surface membranes.