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Unknown Protein Sample Q: I wonder to know the modification of this protein.

Acetylation. Methylation. Phosphorylation. Hydroxylation. Unknown Protein Sample Q: I wonder to know the modification of this protein. Carboxylation. Prenylation. Glycosylation. ADP-ribosylation. glycophospholipid. myristylatopm. Post-translational modification of a desired protein.

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Unknown Protein Sample Q: I wonder to know the modification of this protein.

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  1. Acetylation Methylation Phosphorylation Hydroxylation Unknown Protein Sample Q: I wonder to know the modification of this protein. Carboxylation Prenylation Glycosylation ADP-ribosylation glycophospholipid myristylatopm

  2. Post-translational modification of a desired protein Glycosylation_ glycan structure Unknown Protein Test modification type negative Lectin / Con A positive Glycoprotein Chemically release O glycan Enzymatically release N glycan O glycan pool N glycan pool RP-HPLC charge size MALDI-TOF +/- mode Glycan pool Complex profile Simple profile MS2 for definite structure

  3. Post-translational modification of a desired protein Phosphorylation Unknown Protein Test modification type negative ImmunoAssay (Anti-phosphoTyr/Ser/Thr Antibodies) Dephosphorylation by Phosphatase (SDS-PAGE mobility shift) positive Phosphoprotein Cloning and Site-directed mutagenesis Tendon Mass Phosphorylated residue undeterminable Phosphopeptide Database Hit Protein Candidates Immunoassay method/ dephosphorylation method Phosphorylated residue determinable Specific residue phosphorylation determined

  4. Post-translational modification of a desired protein Acetylation Unknown Protein Test modification type negative ImmunoAssay (commercial acetylated-Lysine monoclonal Antibodies) Deacetylation by deacetylase (SDS-PAGE mobility shift) positive Acetylated protein MALDI-TOF Mass Cloning and Site-directed mutagenesis ESI-ion trap mass Acetylated residue undetectable Protein Candidates Immunoassay method/ deacetylation method acetylated residue Specific residue acetylation determined

  5. Modifications occur • by addition of other groups: • or by isomerization of residues. • L-ala is converted to D-ala in Dermorphin (a peptide of frog skin). • cis and trans proline are interconverted in a reaction important for protein folding. • cysteines are exchanged by a disulfide exchange protein, also important for folding. • during translation (cotranslational) or after the polypeptide chain has been completed (post-translational).

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