Table I.
Conserved properties of the targeting domains of PTS1- and PTS2-targeted plant peroxisomal proteins
| PTS1 Proteins | PTS2 Proteins | |
|---|---|---|
| Major PTS | [SA][RK][LM]> without AKM> plus SRI> and PRL> | R[LI]x5HL |
| Minor PTS | Canonical PTS1 tripeptides: SKI>, PRM>, PKL>, C[RK]L> | R[QTMAV]x5HL, RLx5H[IF], R[AI]x5HI |
| Noncanonical PTS1 tripeptides: S[MN]L>, SNM>, SRV>, SSM>, ANL> | ||
| Amino acids (in order of abundance) | [SAPC][RKNMS][LMIV]> | R[LIQTMAV]x5H[LIF] |
| Targeting domain | ||
| Size | C-terminal 12 to 15 residues | Approximately 15 residues, thus about three residues on each side of the PTS2 nonapeptide |
| Basic residues | High content at position −4 to −6 | High content in the targeting domain (mostly R) |
| Acidic residues | Low content at position −4 to −6 | Low content at position 1 to 10 |
| Charge and pI | Positive charge and basic pI at position −4 to −6 (or spread over the entire targeting domain) | Positive charge (2.2 ± 0.7) and basic pI |
| Proline | High content at position −4 to −9 | Absence in front of the PTS2 nonapeptide (position −1 to −3) and within the x5 region but high content immediately downstream of the PTS2 (position 10 to 15) |
| Hydrophobic residues | High content in the C-terminal 18 residues (A and L) | High content in front of the PTS2 nonapeptide (position −3 to −1) and within the x5 region (A, L, and V) |
| Secondary structure | n.d. | Short α-helix terminating in the end of the nonapeptide |
n.d., not detected.