title: Aqueous, Unfolded OmpA Forms Amyloid-Like Fibrils upon Self-Association.
abstract: Unfolded outer membrane beta-barrel proteins have been shown to self-associate in the absence of lipid bilayers. We previously investigated the formation of high molecular weight species by OmpA, with both the transmembrane domain alone and the full-length protein, and discovered that the oligomeric form contains non-native β-sheet structure. We have further probed the conformation of self-associated OmpA by monitoring binding to Thioflavin T, a dye that is known to bind the cross-β a structure inherent in amyloid fibrils, and by observing the species by electron microscopy. The significant increase in fluorescence indicative of Thioflavin T binding and the appearance of fibrillar species by electron microscopy verify that the protein forms amyloid-like fibril structures upon oligomerization. These results are also consistent with our previous kinetic analysis of OmpA self-association that revealed a nucleated growth polymerization mechanism, which is frequently observed in amyloid formation. The discovery of OmpA's ability to form amyloid-like fibrils provides a new model protein with which to study fibrillization, and implicates periplasmic chaperone proteins as capable of inhibiting fibril formation.
authors.affiliation: T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Danoff
authors.affiliation: T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Karen G
authors.initials: KG
authors.lastname: Fleming
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure; D004926:Escherichia coli / Q000737:chemistry* / Q000648:ultrastructure; D007700:Kinetics; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D014867:Water / Q000737:chemistry
chemical_list: D000682:Amyloid; D001425:Bacterial Outer Membrane Proteins; D014867:Water; C078167:OMPA outer membrane proteins