Table 3.
The most critical posttranslational modifications detected in plants [43].
| Type of PTM (Reversible If Asterisk) | Enzymatic or Spontaneous (Nonenzymatic) | Comment on Subcellular Location and Frequency |
|---|---|---|
| Phosphorylation (His, Tyr, Ser, Asp, Thr) | Enzymatic | Phosphorylation of His and Asp have low frequency |
| S-Nitrosylation (Cys) and nitration* (Tyr) | Spontaneous (RNS), but reversal by thioredoxins is enzymatic for Cys | Throughout the cell |
| Acetylation (Lys ε-amine, N-terminal α-amine) | Enzymatic | In mitochondria, very little N-terminal acetylation, but high Lys acetylation; Lys acetylation correlates to [acetyl-CoA] |
| Deamidation (Asn, Gln) | Spontaneous, but isoAsp reversal is enzymatic by isoAsp methyltransferase | Throughout the cell |
| Lipidation (S-acetylation,N-myristoylation*, prenylation*; Gly, Cys, Trp, Lys, N terminal) | Enzymatic | Not (or not often) within plastids, peroxisomes, mitochondria |
| N-Linked glycosylation (Asp); O-linked glycosylation (Thr, Lys, Trp, Ser) | Enzymatic | Only proteins passing through the secretory system; O-linked glycosylation in the cell wall |
| Ubiquitination (N terminal, Lys) | Enzymatic | Not within plastids, peroxisomes, mitochondria |
| Sumoylation (Lys) | Enzymatic | Not within plastids, peroxisomes, mitochondria |
| Carbonylation* (Pro, Thr, Arg, Lys) | Spontaneous (ROS) | High amounts in chloroplast and mitochondria |
| Methylation (Lys, Arg, N terminal) | Enzymatic | Chloroplasts and histones (nucleus); still not fully explored |
| Glutathionylation (Cys) | Enzymatic | High amounts in chloroplasts |
| Oxidation (Cys, Met) | Spontaneous (ROS) and enzymatic (by PCOs), but reversal is enzymatic by thioredoxins, Met sulfoxide reductases, and glutaredoxins, except if double oxidized | High amounts in chloroplast and mitochondria |
| Peptidase* (cleavage peptidyl bond) | Enzymatic | Throughout the cell |
| S-Guanylation (Cys) | Spontaneous (RNS) | Rare; 8-nitro-cGMP is signaling molecule in guard cells |
| Formylation (Met) | Spontaneous, but deformylation by peptide deformylase is enzymatic | All chloroplasts and mitochondria-encoded proteins are synthesized with initiating formylated Met |