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

A glycoprotein fraction (GP-II) has been isolated from the vitelline membrane of hen's egg and its physicochemical properties clarified. GP-II is composed of polypeptide (92%), neutral sugar (4%), hexosamine (3.3%), and sialic acid (0.6%). The constituent neutral sugars of this glycoprotein are fucose, mannose, and galactose, in a molar ratio of 2:6:5. An interesting feature of the amino acid composition of GP-II is the high proportion of proline. GP-II exists in an aggregated form and is hydrophobic in nature. Upon velocity sedimentation in 0.5% SDS solution, it showed a hypersharp boundary with an apparent sedimentation coefficient of 5.6 S. Reduction of GP-II, however, gave a single component of 3.6 S which seems to be a subunit of GP-II.

Macromolecular components of the vitelline membrane of hen's egg. I. Membrane structure and its deterioration with age.

The vitelline membrane of hen's egg has been successfully solubilized in sodium dodecyl sulfate (SDS), guanidine hydrochloride and urea solutions, and its macromolecular components examined. SDS-gel electrophoresis of the membrane solution revealed the presence of three major components designated I, II, and III, all containing carbohydrate and protein. The approximate molecular weights of components I and II were 32,000 and 260,000, respectively, and the sedimentation coefficients were 2.2S and 4.3S. Component III was in an aggregated form which disintegrated into smaller components upon reduction with 2-mercaptoethanol. It was found that component II (4.3S component) deteriorated during storage of the egg with the concomitant formation of degraded components. The loss of this component was accompanied by a gradual decrease of the neutral sugar content of the vitelline membrane. On the basis of these data, the membrane structure and its deterioration during storage are discussed.

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.