Figure 3.

Key Features of All Peptide Types Based on Representative Examples.

Peptides derived from nonfunctional precursors can be classified in three subgroups: (1) PTM peptides, (2) Cys-rich peptides, and (3) non-Cys-rich/non-PTM peptides. PTM peptides are characterized by specific posttranslational modifications, such as Pro hydroxylation (orange), glycosylation (asterisk), and Tyr sulfation (blue). Cys-rich peptides carry at least two Cys residues to form stable disulfide bridges (square brackets). Non-Cys-rich/non-PTM peptides are not characterized by specific PTM or two or more Cys. Peptides can also be formed from functional precursors or directly translated from sORFs (<100 amino acids) in case no protein precursor is involved in the maturation process. To illustrate the features of all peptide types, the amino acid sequence of a representative mature peptide and the main characteristics of its 3D structure are shown. Additionally, dominant residues (bold), such as Pro, Gly, Lys, Cys, or Tyr, and conserved motifs (underlined) are indicated in the amino acid sequences of these representative peptides. Arabidopsis thaliana (At), Glycine max (Gm), Helianthus annuus (Ha), Hevea brasiliensis (Hb), Impatiens balsamina (Ib), Mirabilis jalapa (Mj), Medicago truncatula (Mt), Oryza sativa (Os); Petunia hybrida (phyb), SUCROSE CONTROL-peptide (SC-peptide); Solanum lycopersicum (Sl), Stellaria media (Sm), Solanum tuberosum (St), Torenia fournieri (Tf), Vigna unguiculata (Vu), Zea mays (Zm). nd, not determined.