title: Unzipping a functional microbial amyloid.
abstract: Bacterial and fungal species produce some of the best-characterized functional amyloids, that is, extracellular fibres that play key roles in mediating adhesion and biofilm formation. Yet, the molecular details underlying their mechanical strength remain poorly understood. Here, we use single-molecule atomic force microscopy to measure the mechanical properties of amyloids formed by Als cell adhesion proteins from the pathogen Candida albicans. We show that stretching Als proteins through their amyloid sequence yields characteristic force signatures corresponding to the mechanical unzipping of β-sheet interactions formed between surface-arrayed Als proteins. The unzipping probability increases with contact time, reflecting the time necessary for optimal inter β-strand associations. These results demonstrate that amyloid interactions provide cohesive strength to a major adhesion protein from a microbial pathogen, thereby strengthening cell adhesion. We suggest that such functional amyloids may represent a generic mechanism for providing mechanical strength to cell adhesion proteins. In nanotechnology, these single-molecule manipulation experiments provide new opportunities to understand the molecular mechanisms driving the cohesion of functional amyloid-based nanostructures.
authors.affiliation: Institute of Life Sciences & Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Croix du Sud, 1 bte L7.04.01, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: David
authors.initials: D
authors.lastname: Alsteens
authors.forename: Caleen B
authors.initials: CB
authors.lastname: Ramsook
authors.forename: Peter N
authors.initials: PN
authors.lastname: Lipke
authors.forename: Yves F
authors.initials: YF
authors.lastname: Dufrêne
mesh_terms: D058227:Amyloidogenic Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D002176:Candida albicans / Q000737:chemistry*; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000648:ultrastructure*; D055119:Elastic Modulus; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D011489:Protein Denaturation; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D058227:Amyloidogenic Proteins; D015815:Cell Adhesion Molecules