title: Structural basis for pore-forming mechanism of staphylococcal α-hemolysin.
abstract: Staphylococcal α-hemolysin (α-HL) is a β-barrel pore-forming toxin (PFT) expressed by Staphylococcus aureus. α-HL is secreted as a water-soluble monomeric protein, which binds to target membranes and forms membrane-inserted heptameric pores. To explore the pore-forming mechanism of α-HL in detail, we determined the crystal structure of the α-HL monomer and prepore using H35A mutant and W179A/R200A mutant, respectively. Although the overall structure of the monomer was similar to that of other staphylococcal PFTs, a marked difference was observed in the N-terminal amino latch, which bent toward the prestem. Moreover, the prestem was fastened by the cap domain with a key hydrogen bond between Asp45 and Tyr118. Prepore structure showed that the transmembrane region is roughly formed with flexibility, although the upper half of the β-barrel is formed appropriately. Structure comparison among monomer, prepore and pore revealed a series of motions, in which the N-terminal amino latch released upon oligomerization destroys its own key hydrogen bond between Asp45-Tyr118. This action initiated the protrusion of the prestem. Y118F mutant and the N-terminal truncated mutant markedly decreased in the hemolytic activity, indicating the importance of the key hydrogen bond and the N-terminal amino latch on the pore formation. Based on these observations, we proposed a dynamic molecular mechanism of pore formation for α-HL.
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan.
authors.forename: Takaki
authors.initials: T
authors.lastname: Sugawara
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan.
authors.forename: Daichi
authors.initials: D
authors.lastname: Yamashita
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan; Faculty of Advanced Life Science, Hokkaido University, Sapporo, 060-0810, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Kato
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Peng
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan.
authors.forename: Junki
authors.initials: J
authors.lastname: Ueda
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kaneko
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kamio
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan; Faculty of Advanced Life Science, Hokkaido University, Sapporo, 060-0810, Japan. Electronic address: tanaka@sci.hokudai.ac.jp.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan; Faculty of Advanced Life Science, Hokkaido University, Sapporo, 060-0810, Japan.
authors.forename: Min
authors.initials: M
authors.lastname: Yao
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004912:Erythrocytes / Q000187:drug effects*; D006460:Hemolysin Proteins / Q000737:chemistry*; D006461:Hemolysis; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D009154:Mutation; D017434:Protein Structure, Tertiary; D011817:Rabbits; D013211:Staphylococcus aureus / Q000378:metabolism / Q000472:pathogenicity; D013329:Structure-Activity Relationship
chemical_list: D001427:Bacterial Toxins; D006460:Hemolysin Proteins; C021091:staphylococcal alpha-toxin
keywords: Crystal structure; Pore-forming toxin; Staphylococcal α-hemolysin