jbc294(5)_1590.pdf 4.14 MB
Miyawaki, Shiori Graduate School of Sustainability Science, Tottori University
Uemura, Yumi Department of Engineering, Tottori University
本郷 邦広 Graduate School of Sustainability Science, Tottori University / Department of Engineering, Tottori University / Center for Research on Green Sustainable Chemistry, Tottori University 研究者総覧 KAKEN
河田 康志 Graduate School of Sustainability Science, Tottori University / Department of Engineering, Tottori University / Center for Research on Green Sustainable Chemistry, Tottori University 研究者総覧 KAKEN
small heat shock protein (sHsp)
The periplasmic small heat shock protein HdeA from Escherichia coli is inactive under normal growth conditions (at pH 7) and activated only when E. coli cells are subjected to a sudden decrease in pH, converting HdeA into an acid-denatured active state. Here, using in vitro fibrillation assays, transmission EM, atomic-force microscopy, and CD analyses, we found that when HdeA is active as a molecular chaperone, it is also capable of forming inactive aggregates that, at first glance, resemble amyloid fibrils. We noted that the molecular chaperone activity of HdeA takes precedence over fibrillogenesis under acidic conditions, as the presence of denatured substrate protein was sufficient to suppress HdeA fibril formation. Further experiments suggested that the secondary structure of HdeA fibrils deviates somewhat from typical amyloid fibrils and contains α-helices. Strikingly, HdeA fibrils that formed at pH 2 were immediately resolubilized by a simple shift to pH 7 and from there could regain molecular chaperone activity upon a return to pH 1. HdeA, therefore, provides an unusual example of a “reversible” form of protein fibrillation with an atypical secondary structure composition. The competition between active assistance of denatured polypeptides (its “molecular chaperone” activity) and the formation of inactive fibrillary deposits (its “fibrillogenic” activity) provides a unique opportunity to probe the relationship among protein function, structure, and aggregation in detail.
American Society for Biochemistry and Molecular Biology
JOURNAL OF BIOLOGICAL CHEMISTRY
© 2019 Miyawaki et al. Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc.
Miyawaki Shiori, Uemura Yumi, Hongo Kunihiro, et al. Acid-denatured small heat shock protein HdeA from Escherichia coli forms reversible fibrils with an atypical secondary structure. JOURNAL OF BIOLOGICAL CHEMISTRY. 2019. 294(5). 1590-1601. doi:10.1074/jbc.RA118.005611
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