Free online lectures by Biochemistry Club
Post Translational Modifications: Trimming, Covalent attachments, Protein folding and Degradation(by Ubiquitination)
- Many polypeptide chains are covalently modified.
- These are modified either while they are still attached to the ribosome, known as Cotranslational modifications, or
- After their synthesis has been completed. These are called Post translational modifications,
- These modifications may include removal of part of the translated sequence or
- The covalent addition of one or more chemical groups required for protein activity.
- These modifications are:
- Covalent attachments
- Protein folding
- Protein degradation.
- The Precursor molecules (Proteins that are synthe4sized) are not functionally active.
- Some portions or parts of the protein chain must be removed.
- This function is carried out by specialized known as Endoproteases.
- This removal of a part from the chain results in the release of an active molecule.
- For example Insulin, Angiotensin
2. Covalent Attachments
- The newly formed Proteins may be activated or inactivated by the covalent attachment of a variety of chemical groups.
- These include:
- Phosphorylation: Phosphorylation occurs on the hydroxyl groups of serine; threonine; or, less frequently, tyrosine residues.
- Glycosylations: almost all proteins in the body are glycosylated except 3 types of proteins.
- Hydroxylations: also occurs in various proteins.
3. Protein Folding
- Proteins after synthesis, must fold to assume their functional, native state.
- Folding can be spontaneous (as a result of the primary structure) or
- Facilitated by proteins known as chaperones….
FOR COMPLETE LESSON ALONG WITH DIAGRAMS PLEASE CLICK THE GENETICS TAB IN THE DROP DOWN MENU OF BIOCHEMSITRY II. THEN CLICK CURRICUM