This document discusses post-translational modifications in proteins. It begins with an introduction explaining that proteins undergo folding and modifications after translation to become functional. It then covers various types of post-translational modifications like the role of chaperones in protein folding, enzymes that catalyze folding like protein disulfide isomerase, and protein cleavage involved in maturation. Other modifications discussed are glycosylation, the addition of carbohydrates, and attachment of lipids. The document concludes that post-translational modifications are important for protein maturation and function.

1. post translational modification in protein
cause and consequence
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. Synopsis
•Translation
•Introduction
•History
•Principle
•Post translational processing
• Chaperons
• Enzymes
• Glycosylation and attachment of lipid
•Conclusion
•References

3. Translation
A polypeptide chain is synthesized by a complex
process called translation in which the assembly of
amino acid in a particular sequence is dictated by
messenger RNA.
DNA
transcription
mRNA
translation
protein

4. Introduction
 For making linear polypeptide chain of amino
acid (primary protein) functional, certain folding
and modifications take place in it which are called
post translational modifications.

5. History
This was initially established by Christian Afinsen.
Principle
The classic principle of protein folding is that all
information required for a protein to adopt the
correct three dimensional conformation is provided
by its amino acid sequence.
The proper folding of proteins with in cells is
mediated by the activities of other protein.

6. Modification in protein
Protein is only functional when it is in folded state.
After translation formed protein is linear so it do not
have any function. For its folding certain enzymes
and protein are required. So various modifications
occur in this nascent polypeptide chain.

7. Types of modification
1 Chaperones
Protein that helps in folding of other protein.
Ron Laskey- first discovered.
Catalyze protein folding.
Two family : Hsp70 and chaperonins.

9. 2 Enzymes that catalyze protein folding
#Protein disulfide isomerase- catalyzes disulfide bond
formation between cysteine residues of polypeptide
chain.
Most abundant in endoplasmic reticulum.
#peptidyl prolyl isomerase – prefering of proline to cis
form can be a limiting factor for folding,so this
enzyme convert cis form of proline to trans form and
help in folding.

10. The action of protein disulfide isomerase
The action of peptidyl
prolyl isomerase

11. 3 Protein cleavage
Cleavage of the polypeptide chain is an important
step in the maturation of many protein.
Also called proteolysis.
Ex.-removal of initiator methionine from the amino
terminus and attachment of other groups.
• Tanslocation of many protein across the
membranes.
• Active enzymes and hormones form via cleavage of
larger precursor.

12. Translocation through cleavage

13. Proteolytic processing of insulin

14. Glycosylation
Addition of carbohydrates.
Glycoprotein are usually found in cell surface.
Glycoprotein have structural , signaling role.
There are two basic types of glycosylation which occur on:
•asparagines (N-linked, see (a) below) and
•serines and threonines (O-linked, see (b) below)

15. Attachment of lipids
Some protein are modified by the attachment of
lipid to polypeptide chain.

16. conclusions
• Post translational modification are very important
for the maturation of protein.
• They make the protein functional and help in
translocation of this protein to their required
places.

17. References
Cell biology( G. M.COOPER and R.E. HAUSMAN)
www.studymode.com
http://en.wikipedia.org