Gene-guided identifications of a structure-chimeric cyclotide viphi I from Viola philippica: potential functions against cadmium and nematodes.

The cyclic peptides, cyclotides, are identified mostly with 29~31-aa (amino acid residues) but rarely with ≥ 34-aa in plants. Viola philippica is a well-known medicinal plant but a rare metallophyte with cyclotides. A hypothesis was hence raised that the potential novel 34-aa cyclotide of Viola philippica would clearly broaden the structural and functional diversities of plant cyclotides. After homology-cloning the cyclotide precursor gene of VpCP5, a 34-aa cyclotide (viphi I) was identified to be larger than 22 other known cyclotides in V. philippica. It had a chimeric primary structure, due to its unusual loop structures (8 residues in loop 2 and 6 residues in loop 5) and aa composition (3 E and 5R), by using phylogenetic analyses and an in-house cyclotide analysis tool, CyExcel_V1. A plasmid pCYC-viphi_I and a lab-used recombinant process were specially constructed for preparing viphi I. Typically, 0.12 or 0.25mgml

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Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Conflict of interests The authors declare that they have no conflict of interest.