Molecular Architecture of PSMα1 Functional Amyloids

Abstract

Biofilms are structurally and functionally complex networks of bacteria and nanoscale macromolecules that play an important role in a myriad of settings from personal health and agriculture to power productions and fuel storage. Amyloid nanofibers are integral components of many biofilms and serve various purposes ranging from virulent to structural. Nonetheless, the precise characterization of bacterial amyloid nanofibers has been elusive, with incomplete and contradicting results. The present work focuses on the molecular details and characteristics of PSMα1 derived functional amyloids present in Staphylococcus aureus biofilms, using a combination of computational and experimental techniques. Results from molecular dynamics simulations, guided and supported by a variety of experiments, show that nanoscale nanofibers present a helical structure formed by two-protofilament PSMα1 amyloid nanofibers. PSMα1 peptides assembles into cross-β sheet structures with an average diameter of about 12 nm, adopting a left-handed helical structure with a periodicity of approximately 72 nm. Strikingly, the chirality of the self assembled nanofibers, an intrinsic geometric property of its constituent peptides, is central in determining the growth and shape of the fibers. The presented findings provide structural insights into the properties of the functional amyloids, hypothesize the role of chirality on the formation of fibers, and aid in strategies for the design of anti-amyloid compounds.

A Multiphysics Modeling of Electromagnetic Signaling Phenomena at kHz-GHz Frequencies in Bacterial Biofilms

“…As it is unclear if only specific aggregates can be responsible for bacterial communication, we analyzed the properties (i.e., electric dipole and geometry) of different candidate aggregates of PSMα1 peptides in both α-helical and β-sheet structure. To this end, we used MD simulations to generate several plausible structures based on biological evidence and compared the properties of these structures with measurements of fibers generated from pure PSMα1 solutions [43] (Fig. 2(a)).…”