Identification of inhibitors of protein-protein interactions essential for virulence in pathogenic bacteria

Abstract

There is a continuous requirement for broad-spectrum post-exposure antibiotic therapeutics. Meeting this challenge relies on the production of compounds that successfully disrupt bacterial systems identified as both conserved and essential. Here, inhibitors of protein-protein interactions involved in the Phage shock protein response and toxin internalisation, within Burkholderia pseudomallei and Bacillus anthracis, respectively have been identified. This was achieved using a high-throughput screen that combines a bacterial reverse two-hybrid system and an intein-mediated method for the generation of cyclic peptide libraries.

A reverse two-hybrid system for Burkholderia pseudomallei PspA homodimerisation was constructed, alongside a heterodimeric system for the interaction between Bacillus anthracis protective antigen and the mammalian receptor, capillary morphogenesis gene-2. From both systems a series of peptide sequences were identified with potential inhibitory activity within the reverse two-hybrid system. These compounds were synthesised and their activity assessed using a selection of in vitro assays.

This study identified two cyclic peptides sequences active in the reverse two-hybrid system against PspA oligomerisation; which were not active in vitro. In contrast, three linear peptides were isolated that demonstrated the ability to disrupt the interaction between protective antigen and the mammalian receptor, with one binding specifically to the receptor. This linear inhibitor provides the foundation for the development of a more potent antimicrobial for the arsenal against Bacillus anthracis.

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Identifiers

ORCID for Ali Tavassoli: orcid.org/0000-0002-7420-5063

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