Glycoprotein Structure Function Relationship: Study of Epithelial Cell Secretion

Abstract

Glycoproteins are polymers in which proteins and carbohydrates are covalently linked, and in which carbohydrates contribute to major biological functions. Glycoproteins are abundantly distributed in microorganisms, plants, animals and humans. There are sufficient indications to suggest that the carbohydrate moiety of the glycoprotein performs significant biological roles such as biological recognition. i.e., specification of blood type, control of the lifetime of glycoproteins in the circulatory system, stage specific differentiation, control of glycoprotein uptake by the cells, acceptors for carbohydrate or protein components and protection of exposed tissue from invasive organisms or molecules. This capability of the carbohydrate arises from the great variety of oligosaccharides that can be formed from a relatively small number of monosaccharides. Oligosaccharide chains can influence the ability of the protein moiety of the glycoprotein to fold properly. The transfer, cotranslational event, of oligosaccharide having the structure (Glc)₃ (Man)₉(GlcNAc)₂ to an aspargine residue of the protein during the biosynthesis in the endoplasmic reticulum may be essential for the protein to acquire correct tertiary structure. Inhibition studies of protein glycosylation support the concept that carbohydrate chains influence the conformation of proteins.