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Protein
Modification
Glycosylation is perhaps the most common and
versatile post-translational modification of proteins. It is
estimated that well over one-half of all mammalian proteins are
glycosylated. The roles of protein glycans, whether N- or O-linked
forms, are varied. Glycan is required for the biological function of
certain proteins, such as,
1. The Fc-effector function of immunoglobulin G (IgG).
2. The regulated clearance of the glycohormone lutropin (LH),
3. The targeting of lysosomal enzymes and,
4. Controlling the circulation lifetime of glycoprotein drugs (for
example, erythropoietin)
Glycans can also serve as:
- Recognition targets for their
complementary binding proteins, the lectins.
- Serving as sites of attachment by microbes
and toxins, and often constitute the first contact point between
pathogen and host.
- Protecting proteins from proteolytic
enzymes.
- Promoting protein foldinginto proper
tertiary and quaternary structure.
- Modulating the biological activities of
protein.
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