Peptide Inhibitors of the <i>Escherichia coli</i> DsbA Oxidative Machinery Essential for Bacterial Virulence

One approach to address antibiotic resistance is to develop drugs that interfere with bacterial virulence. A master regulator of virulence in Gram-negative bacteria is the oxidative folding machinery comprising DsbA and DsbB. A crystal structure at 2.5 Å resolution is reported here for <i>Escherichia coli</i> DsbA complexed with PFATCDS, a heptapeptide derived from the partner protein <i>Escherichia coli</i> DsbB. Details of the peptide binding mode and binding site provide valuable clues for inhibitor design. Structure–activity relationships for 30 analogues were used to produce short peptides with a cysteine that bind tightly to EcDsbA (<i>K</i>_d = 2.0 ± 0.3 μM) and inhibit its activity (IC₅₀ = 5.1 ± 1.1 μM). The most potent inhibitor does not bind to or inhibit human thioredoxin that shares a similar active site. This finding suggests that small molecule inhibitors can be designed to exploit a key interaction of EcDsbA, as the basis for antivirulence agents with a novel mechanism of action