Macromolecular components of the vitelline membrane of hen's egg. II. Physicochemical properties of glycoprotein I.

Of the three major macromolecular components of the vitelline membrane of hen's egg, the lowest molecular weight component (previously designated component I) has been studied and its physicochemical properties clarified. The molecular weight of this component is 27,000 and its chemical composition is typical of a glycoprotein, consisting of protein (91%), total hexose (4.4%), hexosamine (glucosamine 2.3%; galactosamine 0.7%), and sialic acid (1.7%). Uronic acid was not found. The molar ratios of the constituent neutral sugars of this glycoprotein (GP-1) are as follows: fucose 3, mannose 5, galactose 5, glucose 1, and xylose 1. The amino acid profile shows a relatively high proportion of hydrophobic amino acids (39%), which may partly account for the insolubility of GP-I in water.