A Cactus‐Derived Toxin‐Like Cystine Knot Peptide with Selective Antimicrobial Activity

Abstract

Naturally occurring cystine knot peptides show a wide range of biological activity, and as they have inherent stability they represent potential scaffolds for peptide-based drug design and biomolecular engineering. Here we report the discovery, sequencing, chemical synthesis, three-dimensional solution structure determination and bioactivity of the first cystine knot peptide from Cactaceae (cactus) family: Ep-AMP1 from Echinopsis pachanoi. The structure of Ep-AMP1 (35 amino acids) conforms to that of the inhibitor cystine knot (or knottin) family but represents a novel diverse sequence; its activity was more than 500 times higher against bacterial than against eukaryotic cells. Rapid bactericidal action and liposome leakage implicate membrane permeabilisation as the mechanism of action. Sequence homology places Ec-AMP1 in the plant C6-type of antimicrobial peptides, but the three dimensional structure is highly similar to that of a spider neurotoxin.

Toxin structures as evolutionary tools: Using conserved 3D folds to study the evolution of rapidly evolving peptides

“…Aligned sequences are identified according to their PDB accession code. A: alpha‐amylase inhibitor (PDB 1HTX; ), gurmarin (PDB 1C4E; ), Ep‐AMP1 (PDB 2MFS; ), leginsulin (PDB 1JU8; ), and MCoCC‐1 (PDB 2KNP; ). B: κ‐hexatoxin‐Hv1c (PDB 1DL0; ), ω‐hexatoxin‐Hv1a (PDB 1AXH; ), κ‐theraphotoxin‐Gr1a (PDB 1D1H; ), δ‐hexatoxin‐Ar1a (PDB 1QDP; ), and ω‐agatoxin‐Aa4b (PDB 1AGG; ).…”

In Silico Structural Evaluation of Short Cationic Antimicrobial Peptides

“…NMR data were obtained in the absence of micelles and similarity decreases over simulation time, Figure S10: The conformations centroids of the less populated clusters after hierarchical clustering of the predicted structures of cationic peptides with activity against Gram negative bacteria. References [11,12,14,15,16,18,19,20,21,22,31,33,34,37,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,…”

Expanding the structural atlas of peptide toxins

“…The performance of DISH and the effect of adding its predicted restraints to 3D structures computations were evaluated on three examples: the anti-microbial Ep-AMP1 peptide from the Echinopsis pachanoi cactus species (PDB 2mfs), the immunomodulator barrettide A peptide from the marine sponge Geodia barretti (PDB 6cfb) and an engineered cyclic conotoxin cyc-PVIIA from Conus penaceus (PDB 2n8e). [178][179][180] The 3D structures for all peptides have been resolved by 2D NMR spectroscopy and chemical shifts obtained in these studies were used as inputs for the DISH program.…”

“…178 The χ1 angles of three out of the six hemi-cystines have been determined via analysis of coupling constants determined from an E.COSY spectrum and intra residual NOE patterns. 178 Barretide A is a peptide from the marine sponge G. barretti and has been shown to inhibit secretion of cytokines. This peptide contains two disulfide bonds and two anti-parallel β-strands, which form an elongated βsheet.…”

“…Both structures were calculated using the previously derived restraints and additional χ1 and χ2 angles in CNS (SI, Table S4, Table S5). 78,178,179 For Ep-AMP1, there was a significant reduction in the backbone RMSD of the lowest energy structures, from 0.86 Å to 0.55 Å.…”