Peptides containing the PCNA interacting motif APIM bind to the β-clamp and inhibit bacterial growth and mutagenesis
Aina Nedal, Synnøve Brandt Ræder, Bjørn Dalhus, Emily Helgesen, Rune J. Forstrøm, Kim Lindland, Balagra Kasim Sumabe, Jacob H. Martinsen, Birthe B. Kragelund, Kirsten Skarstad, Magnar Bjørås, Marit Otterlei
Abstract
In the fight against antimicrobial resistance, the bacterial DNA sliding clamp, β-clamp, is a promising drug target for inhibition of DNA replication and translesion synthesis. The β-clamp and its eukaryotic homolog, PCNA, share a C-terminal hydrophobic pocket where all the DNA polymerases bind. Here we report that cell penetrating peptides containing the PCNA-interacting motif APIM (APIM-peptides) inhibit bacterial growth at low concentrations in vitro, and in vivo in a bacterial skin infection model in mice. Surface plasmon resonance analysis and computer modeling suggest that APIM bind to the hydrophobic pocket on the β-clamp, and accordingly, we find that APIM-peptides inhibit bacterial DNA replication. Interestingly, at sub-lethal concentrations, APIM-peptides have anti-mutagenic activities, and this activity is increased after SOS induction. Our results show that although the sequence homology between the β-clamp and PCNA are modest, the presence of similar polymerase binding pockets in the DNA clamps allows for binding of the eukaryotic binding motif APIM to the bacterial β-clamp. Importantly, because APIM-peptides display both anti-mutagenic and growth inhibitory properties, they may have clinical potential both in combination with other antibiotics and as single agents.