Aqueous, Unfolded OmpA Forms Amyloid-Like Fibrils upon Self-Association

作者：Danoff Emily J; Fleming Karen G^*

来源：PLos One, 2015, 10(7): e0132301.

DOI：10.1371/journal.pone.0132301

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 beta-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-beta 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.

• 出版日期2015-7-21