Post-translation Modification

A newly formed polypeptide contains a signal sequence, usually on the N-terminus. This signal sequence indicates the place where the polypeptide belongs. Quite often, the translation process is not sufficient enough to produce a functional protein. Post-translational modification and protein folding allows the polypeptide to be functional. Modifications that are essential for functional proteins are as follows:

• Proteolysis: Cutting of the polypeptide chain by protease.
• Glycosylation: Addition of sugars to the protein, forming a glycoprotein. The process happens in the Golgi apparatus.
• Phosphorylation: Addition of a phosphate group, catalyzed by protein kinases.