Figure 4. Structural diversity of AOPs.

A total of 42 AOPs classified into 26 families were identified from O. andersonii. By contrary, only 5 AOPs were identified from O. wuchuanensis. All precursors of these identified AOPs shared a highly conserved motif, which was divided into four parts from the N-terminus to the C-terminus. The first part was an N-terminal hydrophobic signal peptide of about 22 residues in length, followed by an acidic segment that differed in length, ranging from 16–25 residues. The third part was a typical enzyme cleavage site ‘Lys-Arg’, sometimes mutated to ‘Val-Arg’, with the final part a C-terminal section of the mature peptide. The mature peptides confirmed by Edman degradation are underlined. ‘*’indicates that this peptide was identified and reported in our previous study³⁰.