Abstract
The sugar chains of interphotoreceptor retinol-binding protein purified from the interphotoreceptor matrix of bovine eyes were liberated from the polypeptide portion by hydrazinolysis followed by N-acetylation and NaB[3H]4 reduction. The oligosaccharide fraction thus obtained was separated into four acidic fractions by paper electrophoresis. The four acidic fractions were confirmed to be mixtures of mono-, di-, tri-, and tetrasialyloligosaccharides. Both N-acetyl- and N-glycolylneuraminic acids were found as sialic acids of interphotoreceptor retinol-binding protein. The monosialylated oligosaccharide fraction, which accounted for 40 molar per cent of the total oligosaccharides liberated, was a mixture of the following hybrid-type oligosaccharides: (Formula: see text) This is the first time that fucosylated hybrid-type oligosaccharides have been found in any glycoprotein. The di-, tri-, and tetrasialyloligosaccharide fractions were composed of biantennary complex-type oligosaccharides, the outer chains of which are either Sia alpha 2----(3- or 6-linked)Gal beta 1----3(Sia alpha 2----6)GlcNac or Sia alpha 2----(3- or 6-linked)Gal beta 1----4GlcNAc.
Highlights
The sugar chains of interphotoreceptorretinol-binding protein purified from the interphotoreceptor matrix of bovine eyes were liberated from the polypeptide portion by hydrazinolysis followed by N-acetylation and NaBr3HI4reduction
The oligosaccharide fraction obtained was separated into four acidic fractions by paper electrophoresis.The four acidic fractions were confirmed to bemixtures of mono, di, tri,and tetrasialyloligosaccharides.Both N-acetyl- and N-glycolylneuraminic acids were found as sialic acids of interphotoreceptor retinol-binding protein
The di, tri, and tetrasialyloligosaccharide fractions were composed of biantennary complex-type oligosaccharides, the outer chains of which areeitherSiaa2+(3- or 6linked)Gal~1+3(Siaa2+6)GlcNAc or Siaa2+(3- or 6-linked)GalBl-~4GlcNAc
Summary
The sugar chains of interphotoreceptorretinol-binding protein purified from the interphotoreceptor matrix of bovine eyes were liberated from the polypeptide portion by hydrazinolysis followed by N-acetylation and NaBr3HI4reduction. The monosialylated oligosaccharide fraction, which accounted for 40 molar per cent of the total oligosaccharidesliberated, was a mixture of the following hybrid-typeoligosaccharides: ZManal. This is the first time that fucosylated hybrid-type oligosaccharides have beenfoundin any glycoprotein. Fong et al ( 5 ) on the basis of only in the interphotoreceptormatrix [4, 7] In the matrix it lectin-bindingexperiments andpartialstructural analysis binds endogenous retinol, and the amounbtound is greaterin (ll),have suggested thatthechainsare of the complex the light-adapted eye than in the dark-adapted eye [1,2,3]. Endogenously [2] is dependent upon rhodopsin bleaching
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