Synthesis, Structure, and Activity of the Antifungal Plant Defensin PvD₁

Abstract

Available treatments for invasive fungal infections have limitations, including toxicity and the emergence of resistant strains. Therefore, there is an urgent need for alternative solutions. Because of their unique mode of action and high selectivity, plant defensins (PDs) are worthy therapeutic candidates. Chemical synthesis remains a preferred method for the production of many peptide-based therapeutics. Given the relatively long sequence of PDs, as well as their complicated posttranslational modifications, the synthetic route can be considered challenging. Here, we describe a total synthesis of PvD 1 , the defensin from the common bean Phaseolus vulgaris. Analytical, structural, and functional characterization revealed that both natural and synthetic peptides fold into a canonical CSαβ motif stabilized by conserved disulfide bonds. Moreover, synthetic PvD 1 retained the biological activity against four different Candida species and showed no toxicity in vivo. Adding the high resistance of synthetic PvD 1 to proteolytic degradation, we claim that conditions are now met to consider PDs druggable biologicals.

Defensin–lipid interactions in membrane targeting: mechanisms of action and opportunities for the development of antimicrobial and anticancer therapeutics

“…In addition to antibacterial activity, many plant and human defensins have been characterised to have activity against human fungal pathogens such as C. albicans , including NaD1 and HBD-2 via the mechanisms discussed above [ 18 , 48 ] . The common bean defensin PvD1 is active against pathogenic fungi C. albicans , Candida buinensis , Candida tropicalis and Candida parapsilosis at low micromolar concentrations [ 72 ]. PvD1 was also tested in vivo in a C. albicans infection model of Gallieria mellonella (greater wax moth), revealing that treatment with PvD1 significantly increased survival of G. mellonella upon infection with various Candida strains [ 72 ].…”

“…The common bean defensin PvD1 is active against pathogenic fungi C. albicans , Candida buinensis , Candida tropicalis and Candida parapsilosis at low micromolar concentrations [ 72 ]. PvD1 was also tested in vivo in a C. albicans infection model of Gallieria mellonella (greater wax moth), revealing that treatment with PvD1 significantly increased survival of G. mellonella upon infection with various Candida strains [ 72 ].…”

The C-Terminus of Panusin, a Lobster β-Defensin, Is Crucial for Optimal Antimicrobial Activity and Serum Stability

“…LC-MS provided expected masses of 4265 and 2805.6 Da for PaD and Ct_PaD, respectively (Table S1 and Figure S1). Disulfide bridges were generated by the oxidative folding of the linear precursors (hexathiol and tetrathiol, respectively) of PaD and Ct_PaD, under anaerobic thermodynamically controlled conditions [18]. Both oxidation reactions were fast and clean.…”

“…The CYANA program [13] was used to calculate the structure, using distance restrictions derived from intraresidual and sequential NOE cross-peaks and dihedral angle restrictions derived from 1 H and 13 C chemical shifts. The calculation yielded a structure (Figure S9) with a poorly defined N-terminal region (approximately residues 1-11) and a more ordered C-terminal region (approximately residues [12][13][14][15][16][17][18][19][20][21][22]. In this resulting structural ensemble, the disulfide bonds could not be placed, except for a single conformer with a 12-18 disulfide pairing.…”

Use of Defensins to Develop Eco-Friendly Alternatives to Synthetic Fungicides to Control Phytopathogenic Fungi and Their Mycotoxins

“…However, recent advances in peptide synthesis methodologies have paved the way for the successful synthesis of defensins conserving their biological activity and for reducing associated costs. One of the latest successes of defensin chemical synthesis is the production of the PvD1 defensin from the P. vulgaris [ 206 ]. In recent years, genetic engineering, which is the privileged technology for the production of large amounts of proteins, has been subject of intense investigation for the large-scale production of defensins.…”