1. Acid-denatured small heat shock protein HdeA from Escherichia coli forms reversible fibrils with an atypical secondary structure
- Author
-
Yumi Uemura, Kunihiro Hongo, Tomohiro Mizobata, Yasushi Kawata, and Shiori Miyawaki
- Subjects
0301 basic medicine ,Protein Denaturation ,Protein Folding ,Amyloid ,protein fibrillogenesis ,Protein aggregation ,Fibril ,Biochemistry ,Protein Structure, Secondary ,protein aggregation ,03 medical and health sciences ,Heat shock protein ,reversible fibrillation ,Escherichia coli ,Molecular Biology ,Protein secondary structure ,periplasm ,030102 biochemistry & molecular biology ,Chemistry ,Escherichia coli Proteins ,small heat shock protein (sHsp) ,amyloid ,Fibrillogenesis ,Cell Biology ,Periplasmic space ,molecular chaperone ,Hydrogen-Ion Concentration ,030104 developmental biology ,Gram-negative bacteria ,Protein Structure and Folding ,Biophysics ,acid denaturation ,Protein folding ,Acids - Abstract
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.
- Published
- 2018
- Full Text
- View/download PDF