Structural and biological features of a novel plant defensin from Brugmansia x candida

Abstract

Data from both the laboratory and clinic in the last decade indicate that antimicrobial peptides (AMPs) are widely regarded as potential sources of future antibiotics owing to their broad-spectrum activities, rapid killing, potentially low-resistance rate and multidirectional mechanisms of action compared to conventional antibiotics. Defensins, a prominent family of AMPs, have been found in a wide range of organisms including plants. Thailand is a rich source of plants including medicinal plants used therapeutically, however there is no report of defensin from among these plants. In this study, a novel plant defensin gene, BcDef, was successfully cloned from Brugmansia x candida (Bc). BcDef cDNA was 237 bp in length, encoding 78 amino acids with a putative 31-amino acid residue signal peptide at the N-terminal followed by the mature sequence. BcDef shared high sequence identity (78–85%) with Solanaceae defensins and belonged to the class I plant defensins. From homology modeling, BcDef shared a conserved triple stranded β-sheet (β1-β3) and one α-helix (α1) connected by a loop (L1-L3). BcDef1 peptide, designed from the γ-core motifs of BcDef located in loop 3, showed antibacterial activity against both Gram-positive and Gram-negative pathogens with the lowest MIC (15.70 μM) against Staphylococcus epidermidis. This peptide affected cell membrane potential and permeability, and caused cell membrane disruption. Moreover, BcDef1 also exhibited antioxidant activity and showed low cytotoxicity against mouse fibroblast L929 cells. These findings may provide an opportunity for developing a promising antibacterial agent for medical application in the future.

Plant Defensins from a Structural Perspective

“…Several structure-activity studies indicate that the major determinants of the antifungal and antibacterial activity of plant defensins reside in the γ-core motif [ 42 , 54 , 79 , 89 , 99 ]. Furthermore, the γ-core motif peptides derived from defensins RsAFP-2, MtDef4, MtDef5, MsDef1, So-D2, Vu-Def from Vigna unguiculata , BcDef from Brugmansia x candida , PνD1 from P. vulgaris , and the tomato defensin SolyC07g007760 demonstrated antifungal and antibacterial activity at micromolar concentrations [ 21 , 42 , 99 , 100 , 101 , 102 , 103 , 104 ]. Additionally, specific regions within γ-core motifs of MsDef1 and MtDef4 defensins contribute to their different modes of antifungal action [ 105 ].…”

Proteomic response of Escherichia coli to a membrane lytic and iron chelating truncated Amaranthus tricolor defensin

“…Three of these (denoted Atr-DEF1–3) included a highly basic γ-core motif similar to known active synthetic analogs (So-D2, BcDEF, Solyc07g007760, and MtDef4) (Fig. 1 b) [ 8 , 17 , 18 ]. Atr-DEF2 displayed the most positive charge and thus was used to design a synthetic analog spanning the γ-core motif yielding Atr-DEF2(G39-C54) (Fig.…”

“…( b ) Alignment of Atr-DEF2 (predicted mature sequence) with other plant defensins including known sequence of Atr-DEF1 [ 16 ] and predicted mature sequence of Atr-DEF3. Underlined regions have been synthesized as γ-core motif analogs [ 8 , 17 , 18 ]. Cysteines forming disulfide bonds are green, basic residues are red, and acidic residues are blue.…”

Traditional Herbal Medicine in Mesoamerica: Toward Its Evidence Base for Improving Universal Health Coverage

“…Antibacterial (not incl. dermatological pathogens): an isolated peptide showed significant activity against Gram-positive and -negative bacteria in vitro (Kaewklom et al, 2018).…”