title: Amyloid fibril formation in vitro from halophilic metal binding protein: its high solubility and reversibility minimized formation of amorphous protein aggregations.
abstract: Halophilic proteins are characterized by high net negative charges and relatively small fraction of hydrophobic amino acids, rendering them aggregation resistant. These properties are also shared by histidine-rich metal binding protein (HP) from moderate halophile, Chromohalobacter salexigens, used in this study. Here, we examined how halophilic proteins form amyloid fibrils in vitro. His-tagged HP, incubated at pH 2.0 and 58°C, readily formed amyloid fibrils, as observed by thioflavin fluorescence, CD spectra, and transmission or atomic force microscopies. Under these low-pH harsh conditions, however, His-HP was promptly hydrolyzed to smaller peptides most likely responsible for rapid formation of amyloid fibril. Three major acid-hydrolyzed peptides were isolated from fibrils and turned out to readily form fibrils. The synthetic peptides predicted to form fibrils in these peptide sequences by Waltz software also formed fibrils. Amyloid fibril was also readily formed from full-length His-HP when incubated with 10-20% 2,2,2-trifluoroethanol at pH 7.8 and 25°C without peptide bond cleavage.
authors.affiliation: Laboratory of Biochemstry and Bioscience, The United Graduate School of Agricultural Sciences, Kagoshima University, Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Yuhei
authors.initials: Y
authors.lastname: Tokunaga
authors.forename: Mitsuharu
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Masao
authors.initials: M
authors.lastname: Tokunaga
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Arakawa
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sugimoto
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D055353:Chromohalobacter / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D005456:Fluorescent Dyes; D006801:Humans; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D033902:Periplasmic Binding Proteins / Q000737:chemistry*; D011487:Protein Conformation; D012984:Software; D014270:Trifluoroethanol / Q000737:chemistry
chemical_list: D000682:Amyloid; D001426:Bacterial Proteins; D005456:Fluorescent Dyes; D010455:Peptides; D033902:Periplasmic Binding Proteins; C018963:histidine-binding protein; D014270:Trifluoroethanol
keywords: 2,2,2,-trifluoroethanol; acid-hydrolysis; amyloid fibril; halophilic; solubility; thioflavin
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