VOLUME 12 NUMBER 1 (January to June 2019)

by Bea A. Crisostomo^*1, Arnelson Arwin G. Atis², Denise Noelle R. Mirano-Bascos¹, and
Christine C. Hernandez²

¹National Institute of Molecular Biology and Biotechnology, College of Science
     University of the Philippines Diliman, Quezon City, Philippines
²Institute of Chemistry, College of Science, University of the Philippines Diliman,
     Quezon City, Philippines

Knottins are small proteins with at least three disulfide bridges that form a cysteine knot, giving them exceptional stability. These molecules are candidates for developing peptide-based drugs that are envisioned to fill the gap between small-molecule drugs and biologics as they are bioavailable, like small-molecule drugs, and target-specific, like biologics. Plant-derived knottins are able to preserve their stable conformation in the presence of mutations and peptide grafts, making them potential drug scaffolds. Through LC/MS screening of 185 plant extracts from 180 plant species, we identified 6 Philippine plants that produce disulfide-rich peptides structurally related to knottins. Four of these plants were further analyzed using transcriptome screening and we confirmed that Alstonia scholaris, Wrightia pubescens and Tabernaemontana pandacaqui from the Apocynaceae family produce knottin-like peptides similar to previously reported Apocynaceae alpha amylase inhibitors. Given the novelty of their sequences, it is possible that these peptides possess novel functions as well. This is the first report of cysteine knot peptides from W. pubescens and T. pandacaqui. Finally, we showed that LC/MS screening followed by transcriptome analysis is a more efficient workflow for identifying cysteine knot peptides as opposed to LC/MS screening alone.