Structural insights into

Curli are a widespread component of proteobacterial biofilms. They are functional amyloid fibers that aid in structuring the extracellular matrix that surrounds these multicellular communities. As a functional amyloid, they are the product of a dedicated assembly pathway that needs to navigate the cytotoxicity classically associated with most amyloid depositions. Recent breakthroughs in cryo-EM and protein structure prediction have started to shed light on the unique structural principles of curli fibrils. Here, we revisit the recent literature and focus on the consensus model for these remarkable protein fibrils.IMPORTANCEAmyloid fibrils receive enormous interest as instigators of protein aggregation disorders and associated wasting diseases, as functional components of complex biological matrices, including biofilms, and/or as versatile and self-assembling protein scaffolds for protein material applications. Central to each of these phenomena are the structural properties of the component subunits and how they assemble in the amyloid fibril. A thorough understanding of these architectural principles is essential for the rational interference with amyloids, be it inhibitory in the case of disease-associated amyloids, or as a basis for biotechnological applications of functional amyloids.