Reduction by mercaptoethanol and proteolysis of the non-glycosylated peptide region of pig gastric mucus glycoprotein.

Abstract

The native pig gastric mucus glycoprotein was purified free from non-covalently bound protein by a combination of gel-filtration on Sepharose 4B and equilibrium centrifugation in a CsCl gradient (Starkey et al., 1974; Pearson et al., 1981). On reduction with 0.2M mercaptoethanol the native glycoprotein (2 × 106 molecular weight) is split into an average of 4 equal sized subunits (5 × 105 molecular weight) and a 70,000 molecular weight protein fraction. The 70,000 molecular weight protein fraction which contains little or no carbohydrate can be separated from the reduced glycoprotein subunits by equilibrium centrifugation in a CsCl gradient (Allen et al., 1980; Pearson & Allen, 1980). Here we report further investigations on the structure of the non-glycosylated region of glycoprotein defined as that part of the peptide core which is free of carbohydrate and is removed when the molecule is split by proteolysis into 4 subunits of molecular weight 5 × 105 (Scawen & Allen, 1977).