Cell surface-localized CsgF condensate is a gatekeeper in bacterial curli subunit secretion.

Curli are functional amyloids present on the outer membrane of E. coli. CsgF is required for the proper assembly of curli.

Substoichiometric Hsp104 regulates the genesis and persistence of self-replicable amyloid seeds of Sup35 prion domain.

Prion-like self-perpetuating conformational conversion of proteins is involved in both transmissible neurodegenerative diseases in mammals and non-Mendelian inheritance in yeast. The transmissibility of amyloid-like aggregates is dependent on the stoichiometry of chaperones such as heat shock proteins (Hsps), including disaggregases. To provide the mechanistic underpinnings of the formation and persistence of prefibrillar amyloid seeds, we investigated the role of substoichiometric Hsp104 on the in vitro amyloid aggregation of the prion domain (NM-domain) of Saccharomyces cerevisiae Sup35.

Intrinsically disordered proteins in the formation of functional amyloids from bacteria to humans.

Amyloids are nanoscopic ordered self-assemblies of misfolded proteins that are formed via aggregation of partially unfolded or intrinsically disordered proteins (IDPs) and are commonly linked to devastating human diseases. An enlarging body of recent research has demonstrated that certain amyloids can be beneficial and participate in a wide range of physiological functions from bacteria to humans. These amyloids are termed as functional amyloids.

Human Fibrinogen Inhibits Amyloid Assembly of Biofilm-Forming CsgA.

Curli is a biofilm-forming amyloid that is expressed on the surface of Gram-negative enteric bacteria such as Escherichia coli and Salmonella spp. Curli is primarily composed of the major structural subunit, CsgA, and interacts with a wide range of human proteins that contribute to bacterial virulence. The adsorption of curli onto the contact-phase proteins and fibrinogen results in a hypocoagulatory state.

Electrostatic lipid-protein interactions sequester the curli amyloid fold on the lipopolysaccharide membrane surface.

Curli is a functional amyloid protein in the extracellular matrix of enteric Gram-negative bacteria. Curli is assembled at the cell surface and consists of CsgA, the major subunit of curli, and a membrane-associated nucleator protein, CsgB. Oligomeric intermediates that accumulate during the lag phase of amyloidogenesis are generally toxic, but the underlying mechanism by which bacterial cells overcome this toxicity during curli assembly at the surface remains elusive.

Site-Specific Fluorescence Depolarization Kinetics Distinguishes the Amyloid Folds Responsible for Distinct Yeast Prion Strains.

The prion determinant of a yeast prion protein, Sup35NM, assembles into β-rich amyloid fibrils that switch the nonprion [psi] state to the prion [PSI] state of yeast. Previous studies showed that two distinct forms of amyloids (Sc4 and Sc37), generated in vitro at two different temperatures (4 and 37 °C), recapitulate the strain phenomenon in Saccharomyces cerevisiae. Sc4 demonstrates a strong [PSI] phenotype, whereas Sc37 shows a weak phenotype.

Characterization of Salt-Induced Oligomerization of Human β2-Microglobulin at Low pH.

Misfolding and amyloid aggregation of human β2-microglobulin (β2m) have been linked to dialysis-related amyloidosis. Previous studies have shown that in the presence of different salt concentrations and at pH 2.5, β2m assembles into aggregates with distinct morphologies.