Animal Biotechnology

POST- TRANSLATIONAL MODIFICATIONS

• A translated polypeptide does not always immediately generate a functional protein (inactive).
• Apart from correct folding and the possible formation of disulfide bonds, there are number of other alterations that may be required for activity. These include cleavage and various covalent modifications.
• Cleavage is very common, especially trimming by amino – and carboxy peptidases, but the removal of internal peptides also occurs.
• Chemical modifications are many and varied and have been shown to take place on the N and C termini, as well as on most of the 20 aminoacid side chains with the exception of Alanine, Glycine. Isoleucine, Leucine, Methionine and Valine.
• The modifications include acetylation, hydroxylation, Phosphorylation, methylation, Glycosylation and even the addition of nucleotides. Often phosphorylation controls the activity of protein.