title: Thermostable direct hemolysin of Vibrio parahaemolyticus is a bacterial reversible amyloid toxin.
abstract: Thermostable direct hemolysin (TDH), a major virulence factor of Vibrio parahaemolyticus, is detoxified by heating at approximately 60-70 degrees C but is reactivated by additional heating above 80 degrees C. This paradoxical phenomenon, known as the Arrhenius effect, has remained unexplained for approximately 100 years. We now demonstrate that the effect is related to structural changes in the protein that produce fibrils. The native TDH (TDHn) is transformed into nontoxic fibrils rich in beta-strands by incubation at 60 degrees C (TDHi). The TDHi fibrils are dissociated into unfolded states by further heating above 80 degrees C (TDHu). Rapid cooling of TDHu results in refolding of the protein into toxic TDHn, whereas the protein is trapped in the TDHi structure by slow cooling of TDHu. Transmission electron microscopy indicates the fibrillar structures of TDHi. The fibrils show both the property of the nucleation-dependent elongation and the increase in its thioflavin T fluorescence. Formation of beta-rich structures of TDH was also observed in the presence of lipid vesicles containing ganglioside G(T1b), a putative TDH receptor. Congo red was found to inhibit the hemolytic activity of TDH in a dose-dependent manner. These data reveal that the mechanism of the Arrhenius effect which is tightly related to the fibrillogenicity of TDH.
authors: Department of Developmental Infectious Diseases, Research Institute, Osaka Medical Center for Maternal and Child Health, 840 Murodo-cho, Izumi, Osaka 594-1101, Japan.
authors: Takashi
authors: T
authors: Fukui
authors: Kentaro
authors: K
authors: Shiraki
authors: Daizo
authors: D
authors: Hamada
authors: Kojiro
authors: K
authors: Hara
authors: Tomoko
authors: T
authors: Miyata
authors: Shinsuke
authors: S
authors: Fujiwara
authors: Kouta
authors: K
authors: Mayanagi
authors: Keiko
authors: K
authors: Yanagihara
authors: Tetsuya
authors: T
authors: Iida
authors: Eiichiro
authors: E
authors: Fukusaki
authors: Tadayuki
authors: T
authors: Imanaka
authors: Takeshi
authors: T
authors: Honda
authors: Itaru
authors: I
authors: Yanagihara
mesh_terms: D000682:Amyloid / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000633:toxicity*; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000737:chemistry; D000818:Animals; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000633:toxicity; D052160:Benzothiazoles; D002942:Circular Dichroism; D003224:Congo Red / Q000737:chemistry; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000633:toxicity; D006358:Hot Temperature; D008954:Models, Biological; D008956:Models, Chemical; D008970:Molecular Weight; D011487:Protein Conformation; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013844:Thiazoles / Q000737:chemistry; D037521:Virulence Factors / Q000737:chemistry / Q000633:toxicity
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D052160:Benzothiazoles; D006460:Hemolysin Proteins; D013844:Thiazoles; D037521:Virulence Factors; C088609:thermostable direct hemolysin-related hemolysin protein, Vibrio parahaemolyticus; C068489:thermostable direct hemolysin; C009462:thioflavin T; D003224:Congo Red