Identifying interaction interface betweenPseudomonasmajor biofilm forming functional amyloid FapC and disordered chaperone FapA during fibrillation deceleration

Abstract

Functional bacterial amyloids (FuBA) are involved in biofilm formation in Pseudomonas aeruginosa. Biofilm forming bacterial colonies are difficult to treat, cause most of the chronic bacterial infections and are relevant in the context of antimicrobial resistance. Here in this work by focusing on the major biofilm forming FapC protein we demonstrate the initial steps of the chaperone aided amyloid formation. Solution NMR spectroscopy gave atomic resolution information on the prefibrillar soluble monomeric FapC that is an intrinsically disordered protein (IPD). Moreover, we show that the chaperone FapA within the same biofilm forming protein operon interacts with FapC. FapA is itself an IDP and remarkably slows down the FapC fibril formation without modifying the final fibril morphology. Monitoring of the small but significant chemical shift perturbations allowed the determination of the interaction interface which was not observed previously. To the best of our knowledge, our work provides the first atomic-level identification of a rather specific interaction of an IDP chaperone, FapA, to modulate and slow-down the functional amyloid protein FapC towards its path to mature fibril formation. Our results establish a better understanding of the functional amyloid formation in bacterial biofilms and its molecular level tuning or prevention by chaperones. We foresee that future therapeutic treatments of biofilms and relevant infections could emerged from these structural and mechanistic insights.