X-ray Crystallographic Structure of a Teixobactin Derivative Reveals Amyloid-like Assembly

Abstract

This paper describes the X-ray crystallographic structure of a derivative of the antibiotic teixobactin and shows that its supramolecular assembly through the formation of antiparallel β-sheets creates binding sites for oxyanions. An active derivative of teixobactin containing lysine in place of allo-enduracididine assembles to form amyloid-like fibrils, which are observed through a thioflavin T fluorescence assay and by transmission electron microscopy. A homologue, bearing an N-methyl substituent, to attenuate fibril formation, and an iodine atom, to facilitate X-ray crystallographic phase determination, crystallizes as double helices of β-sheets that bind sulfate anions. β-Sheet dimers are key subunits of these assemblies, with the N-terminal methylammonium group of one monomer and the C-terminal macrocycle of the other monomer binding each anion. These observations suggest a working model for the mechanism of action of teixobactin, in which the antibiotic assembles and the assemblies bind lipid II and related bacterial cell wall precursors on the surface of Gram-positive bacteria.

The impact of backbone N‐methylation on the structure‐activity relationship of Leu10‐teixobactin

“…In general, N ‐methylation was detrimental to antimicrobial activity, although 11 still retained low potency (MIC = 16 μg/mL). This loss of activity indicates that conformational changes to the N ‐methylated analogues might have occurred and/or hydrogen bonding is critical for the monomeric or multimeric active structure; the latter as proposed by Yang et al, which describes the formation of amyloid‐like assemblies of teixobactin as intrinsic to its mechanism of action.…”

“…Initially, it was purported to be involved in membrane insertion and/or binding directly to the isoprenyl tail of lipid II . Based on crystallographic data, it has recently been put forward that the peptide forms an amyloid‐like assembly and acts as a multivalent receptor for the pyrophosphate moiety in lipid II …”

“…5 Based on crystallographic data, it has recently been put forward that the peptide forms an amyloid-like assembly and acts as a multivalent receptor for the pyrophosphate moiety in lipid II. 6 Several groups have reported the chemical synthesis of both native teixobactin 7,8 and various analogues 9,10 by 9fluorenylmethyloxycarbonyl (Fmoc) solid-phase peptide synthesis (SPPS). To date, three generic synthetic strategies have been established: (a) a stepwise synthesis and solution phase cyclisation 6,8,[11][12][13][14] ; (b) a stepwise synthesis and "on-resin" cyclisation 15,16 ; and (c) a convergent strategy.…”

“…6 Several groups have reported the chemical synthesis of both native teixobactin 7,8 and various analogues 9,10 by 9fluorenylmethyloxycarbonyl (Fmoc) solid-phase peptide synthesis (SPPS). To date, three generic synthetic strategies have been established: (a) a stepwise synthesis and solution phase cyclisation 6,8,[11][12][13][14] ; (b) a stepwise synthesis and "on-resin" cyclisation 15,16 ; and (c) a convergent strategy. 7,17 Effective structureactivity relationship (SAR) studies of teixobactin necessitates a synthetic route that is both rapid and efficient.…”

Dissecting the Binding Interactions of Teixobactin with the Bacterial Cell‐Wall Precursor Lipid II

“…Interest in the peptide's activity and therapeutic potential led to curiosity in synthetic approaches to access teixobactin; with two distinct synthetic routes reported just a year later . Following the initial report, several studies were aimed at understanding the spectrum of antimicrobial activity, structure–activity studies, interrogating the mode of action through modelling, and structural investigations . These studies yielded insight into key residues, modifiable regions, and suspected binding sites of teixobactin to its cellular targets—the bacterial cell wall precursors: lipid II (Figure B) and lipid III.…”