Post translational modification/PTM/protein modifications

POST TRANSLATIONAL MODIFICATION (PTM) SIMPLE & BASIC CONCEPT

1. POST TRANSLATIONAL MODIFICATION BY A.MANOJ KUMAR

2. DEFINISION It is a chemical modification of a protein after its translation. It takes place at certain amino acids residues after the protein is synthesized. Post Translational Modification are essential for normal functioning of the cell. It necessary for Stability of protein Biochemical Activity Protein Targeting (protein localization) Protein signalling(protein-protein interaction)

3. PTMs occur in Golgi Apparatus and Endoplasmic Reticulum MODIFICATION Modification involving peptide bond cleavage Modification of Amino acids Protein folding and chaperones Subunit Aggregation Protein Folding

4. MODIFICATION INVOLVED PEPTIDE BOND CLEAVAGE(Trimming of peptide bond It is specific and well regulated Enzymatic and non – enzymatic Precursor protein(inactive)-Mature active ptn The amino acids residues are removed one by one either from N-terminus or C-terminus end, with the help of the enzyme exopeptidase

5. MODIFICATION OF AMINO ACIDS PHOSPHORYLATION Addition of Phosphate group to serine,threonine and tyrosine LIPIDATION Addition of lipid molecule such as fatty acids to the protein chain UBIQUITINATION Addition of Ubiquitin,to a lysine residue of a target protein, marking it for destraction .

6. ACETYLATION Addition of Acetyl group to the N-terminus of the protein to increase the stability GLYCOSYLATION Addition of sugar molecule to the ‘N’ or ‘O’ atom in an amino acid side chain METHYLTION Addition of methyl group to the amino acid

7. ADDITION OF PROSTHETIC GROUP (CO-FACTOR) Many enzyme function only when it associated with co-factor or prosthetic group The prosthetic group are Biotin,FAD,Haem,Pantothemic acid The tertiary and quaternary structure of protein is attained only when it complexed with some co-factor Iron in case of Haemoglobulin Mg²+ in case of chlorophyll

8. siGNAL MOLECULES Signal molecules are added or removed from the N-terminus end off the protein for the transportation to their specific destination Once a protein has reach its destination the signal molecules is removed

9. MODIFICATION PHOSPHORYLATION GLYCOSYLATION ACYLATION ALKYLATION HYDROXYLATION AMINO ACIDS Ser,Thr,Tyr Asn,Ser,Thr Asn,Gln,Lys Lys, Arg Pro, Lys

10. PROTEIN FOLDING AND CHAPERONS Chaperon are proteins that facilate folding of other proteins Chaperon first discovered in drosophila They are also called as heat shock protein HSP70 AND HSP 60 FUNCTION It prevents the formation of unwanted interaction , that do not provide biological activity Stabilises the interaction Avoids improper folding ,aggregation and precipitation of protein

11. PROTEIN FOLDING AND CHAPERONS

12. Protein splicing The protein consist of Exteins and Inteins An Inteins is a segment of a protein that is able to excise itself and join the remaining portion with the help of peptide bond The protein Splicing is required for convention of inactive protein precursor into biologically active protein It is found in bacteria,Eukaryotes and viruses.

13. Protein splicing

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