Fig. 3
From: Molecular basis for the production of cyclic peptides by plant asparaginyl endopeptidases
The marker of ligase activity (MLA) is present in evolutionary distant AEP ligases. Multiple sequence alignment of functionally verified AEP plant ligases from O. affinis, C. ternatea and P. x hybrida with protease-type AEPs from the same plant species. Overlaid by a magenta bar is the region defined as the marker of ligase activity (MLA), which contains a deletion in the functionally verified ligases from petunia (PxAEP3b) and O. affinis (OaAEP1b and OaAEP3) and is rich in hydrophobic residues in the case of the butelase-1 from C. ternatea. For human AEP (hAEP), a glycosylation site is present within a similarly small MLA region28. Overlaid by a green bar is the Gatekeeper (GK) residue (Cys247, OaAEP1b numbering) identified in OaAEP1 to be important for its in vitro ligase efficiency22. Overlaid in blue is the plant-specific poly-proline loop, which is present in both plant ligase and protease type AEPs but missing from the human AEP (hAEP)
