title: Fibrillation of the major curli subunit CsgA under a wide range of conditions implies a robust design of aggregation.
abstract: The amyloid fold is usually considered a result of protein misfolding. However, a number of studies have recently shown that the amyloid structure is also used in nature for functional purposes. CsgA is the major subunit of Escherichia coli curli, one of the most well-characterized functional amyloids. Here we show, using a highly efficient approach to prepare monomeric CsgA, that in vitro fibrillation of CsgA occurs under a wide variety of environmental conditions and that the resulting fibrils exhibit similar structural features. This highlights how fibrillation is "hardwired" into amyloid that has evolved for structural purposes in a fluctuating extracellular environment and represents a clear contrast to disease-related amyloid formation. Furthermore, we show that CsgA polymerization in vitro is preceded by the formation of thin needlelike protofibrils followed by aggregation of the amyloid fibrils.
authors.affiliation: Interdisciplinary Nanoscience Center, Centre for Insoluble Protein Structures, Department of Molecular Biology, Aarhus University, 8000 Aarhus C, Denmark.
authors.forename: Morten S
authors.initials: MS
authors.lastname: Dueholm
authors.forename: Søren B
authors.initials: SB
authors.lastname: Nielsen
authors.forename: Kim L
authors.initials: KL
authors.lastname: Hein
authors.forename: Poul
authors.initials: P
authors.lastname: Nissen
authors.forename: Matthew
authors.initials: M
authors.lastname: Chapman
authors.forename: Gunna
authors.initials: G
authors.lastname: Christiansen
authors.forename: Per Halkjær
authors.initials: PH
authors.lastname: Nielsen
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Otzen
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry*; D000682:Amyloid / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D020836:Protein Structure, Quaternary
chemical_list: D018829:Adhesins, Bacterial; D000682:Amyloid; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C489688:csgA protein, E coli; C077481:Crl protein, Bacteria