phosphorylation Ph acetylation Ac methylation Me nitrosylation Ni nitration Nt SUMOylation SM ubiquitination Ub neddylation Ne N-linked glycosylation NG O-linked glycosylation OG O-GlcNAc glycosylation OGl O-GalNAc glycosylation OGa glycation Gc C-linked glycosylation CG S-linked glycosylation SG glycophosphatidilinositol attachment GA glycosylation Gl proteolytic cleavage PC caspase cleavage aspartic acid CD hydroxylation Hy palmitoylation Pa prenylation Pr myristoylation My malonylation Ma citrullination Ci succinylation Sc alkylation Al formylation Fo farnesylation Fa oxidation Ox protein-FAD linkage pF ADP-ribosylation AR binding to a nucleotide sequence BN protein-pyridoxal-5-phosphate linkage PP carboxylation Ca pyrrolidone carboxylic acid formation Py sulfation Su amidation Am carbamidation Cb glutathionylation Gt unidentified N-terminal blocking modifications Un GPI-anchor GP L-glutamyl 5-glycerylphosphorylethanolamine eE N6-retinylidene-L-lysine rK L-3-oxoalanine oA O-phosphopantetheine-L-serine pS N6-lipoyllysine lK amino acid modification AM N6-biotinyl-L-lysine bK serine conversion into pyruvic acid Sp N6-carboxylysine cK S-(4a-FMN)-L-cysteine fC dipyrrolylmethanemethyl-L-cysteine mC dehydroalanine hA hypusine HK glutamine deamidation dQ aspartic acid conversion into alanine aA N-pyruvic acid 2-iminyl-L-cysteine iC N6-1-carboxyethyl-L-lysine eK diphthamide DI iodination IO topaquinone formation TQ bromination Br intra-polypeptide disulfide bond formation DB intra-peptide isopeptide bond formation IB isopeptide bond IB thioether bond TB transglutamination TG allysine aK