Molecular grafting can generate bioactivities within the cyclic peptide PDP-23 — ASN Events

Molecular grafting can generate bioactivities within the cyclic peptide PDP-23 (#245)

Fatemeh H. Alipour 1 , Angela Song 1 , Grishma Vadlamani 2 , Jingjing Zhang 2 , Joshua Mylne 2 3 , Richard Clark 1 , K. Johan Rosengren 1
  1. School of Biomedical Sciences, University of queensland, St Lucia, QLD, Australia
  2. School of Molecular Sciences, The University of Western Australia, Crawley, WA, Australia
  3. Centre for Crop and Disease Management, School of Molecular and Life Sciences, Curtin University, Bentley, WA, Australia

The stability of cyclic peptides, coupled with their structural diversity and ability to host an extensive range of bioactivities, make them promising leads for the development of new drugs. PawS-Derived Peptide-23 (PDP-23) is a head-to-tail macrocyclic peptide with two disulfide bonds, identified from seeds of Zinnia elegans. Its unusual fold comprises two b-hairpins connected by hinges that allow the structure to adapt to different environments. In water two PDP-23 molecules form a compact intertwined dimer that buries hydrophobic residues, whereas in membrane mimicking conditions it adopts an open monomeric form that expose them. Here we investigate PDP-23 as a novel scaffold for the grafting of bioactive epitopes. To explore the plasticity of PDP-23 we introduced the bioactive loop of sunflower trypsin inhbitor-1 (SFTI-1) or an integrin binding RGD motif into either of the b-hairpins. Solution NMR spectroscopy revealed that although the variants were unable to dimerise, the structural features of both the graft and scaffold were retained. SFTI-1 hybrid variants showed trypsin inhibitory activity. PDP-23 has previously been used as a cell permeable drug scaffold targeting drug-resistant cancer cells by conjugation of a small molecule that inhibit the drug efflux pump P-glycoprotein and restore sensitivity to chemotherapeutics. Introducing the RGD motif into such PDP-23 conjugates significantly improve their potency, suggesting that the RGD sequence targets the peptide to the membrane of cancer cells and improve cell uptake. In conclusion, this study highlights PDP-23 as a stable and versatile scaffold for molecular grafting of bioactivities and targeted delivery of pharmaceutical payloads.

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