Isolation and partial characterization of the sialoglycoprotein fraction of murine erythrocyte ghosts.

Abstract

With the lithium diiodosalicylate (LIS1) extraction-phenol partition method, a sialoglycoprotein fraction from DBA/2 mouse erythrocyte ghosts was isolated. The Laemmeli system for SDS-PAGE [sodium dodecylsulfate-polyacrylamide gel electrophoresis] resolved this fraction into 4 monomers, of which 2 (gp[glycoprotein]-2.1 and gp-3.1) appeared to be authentic, whereas the other 2 (gp-2.2 and gp-3.2) were probably generated from gp-2.1 and gp-3.1 by limited proteolysis during the isolation procedure. All 4 components contained O-acetylated neuraminic acid residues, were stained with periodic acid-Schiff reagent (PAS) and with Coomassie Brilliant Blue (CB), and were radioiodinated with the lactoperoxidase-glucose oxidase (LPO-GO) method. All monomers, but especially gp-2.1 and gp-3.1, generated characteristic aggregates during solubilization in SDS. The aggregation was enhanced by boiling at high concentrations and was reversed by boiling at low concentrations. The fraction contained a diffuse component present also in ghosts which stained poorly with CB and with PAS and could not be radioiodinated by the LPO-GO technique. SDS-PAGE in the Steck and Yu gel system does not give an accurate separation of the sialoglycoprotein monomers.