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POST TRANSLATIONAL MODIFICATION Presentation Transcript:
1.POST TRANSLATIONAL MODIFICATION
2.Post Translational Modification
Chemical modifications
A key role in functional proteomics
3. By the covalent addition of functional groups to proteins, proteolytic cleavage of regulatory subunits or degradation
The functional diversity proteome.
4.Phospharylation
Addition of a phosphate(PO43-) group.
Phosphorylation protein enzymes
Phosphorylation is associated with respiration and photosynthesis.
Metabolic Energy energy-rich phosphate bonds (ATP).
5.Oxidative phosphorylation
ATP formation = respiratory uptake of oxygen.
ADP + HPO42- + NADH + 1/2 O2 + 2H+ ? ATP + NAD+ + 2 H2O
6.Glycosylation
A carbohydrate, i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor).
Structural and functional roles in membrane and secreted proteins.
Enzyme-directed site-specific process
7.Types of glycosylation:
N-linked glycans
O-linked glycans
phospho-serine
C-linked glycans
Glypiation
8.Ubiquinitation
Enzymatic process
COO- Glycine from the di-glycine motif in the activated ubiquitin forms an amide bond to the epsilon amine of the lysine in the modified protein.
Steps:
Activation of ubiquitin
Transfer of ubiquitin
Isopeptide bond between a lysine of the target protein and the C-terminal glycine of ubiquitin.
9.S-Nitrosylation
NO + Cysteine S-Nitrothiols(SNOs)
Used To:
Cells to stabilize proteins
Regulate gene expression
Provide NO donors
The generation, localization, activation and catabolism of SNOs.
SNOs ? Short Life in Cytoplasm
Therefore; Stored in membranes, vesicles, the interstitial space and lipophilic protein folds.
10.Methylation
Transfer of methyl groups to N or O2 (N- and O-methylation)to amino acid side chains.
Hydrophobicity of protein.
Methyltransferases.
S-adenosyl methionine(SAM)?Primary donor.
N-methylation is irreversible.
O-methylation is potentially reversible.
11.The transfer of an acetyl group to nitrogen.
Occurs in all eukaryotic proteins.
12.Lipidation
To target proteins to Lipid membranes in organelles
Endoplasmic reticulum [ER]
Golgi apparatus
Mitochondria
Vesicles (endosomes, lysosomes)
Plasma membrane.
13.Types of Lipidation
C-terminal glycosyl phosphatidylinositol (GPI) anchor
N-terminal myristoylation
S-myristoylation
S-prenylation
14.To give proteins a hydrophobic handle for membrane localization.
Group is a 14-carbon saturated fatty acid (C14)
Facilated By N-myristoyltransferase (NMT) & uses myristoyl-CoA (substrate) to
?myristoyl group + N-terminal glycine.
15.GPI anchors
Cell surface proteins plasma membrane.
Hydrophobic moieties are prepared in the ER.
Often localized to cholesterol- and sphingolipid-rich lipid rafts
Reversible
Source: Power Point Presentations
