Journal
PROTEIN SCIENCE
Volume 20, Issue 2, Pages 448-456Publisher
WILEY
DOI: 10.1002/pro.579
Keywords
staphylococcal alpha-hemolysin; 2-methyl-2,4-pentanediol (MPD); heptamer formation; crystal structure
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Funding
- Ministry of Education, Science, Sports, and Culture of Japan
- Grants-in-Aid for Scientific Research [23380046, 23658066] Funding Source: KAKEN
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Staphylococcal a-hemolysin is expressed as a water-soluble monomeric protein and assembles on membranes to form a heptameric pore structure. The heptameric pore structure of alpha-hemolysin can be prepared from monomer in vitro only in the presence of deoxycholate detergent micelles, artificially constructed phospholipid bilayers, or erythrocytes. Here, we succeeded in preparing crystals of the heptameric form of alpha-hemolysin without any detergent but with 2-methyl-2,4-pentanediol (MPD), and determined its structure. The structure of the heptameric pore was similar to that reported previously. In the structure, two molecules of MPD were bound around Trp179, around which phospholipid head groups were bound in the heptameric pore structure reported previously. Size exclusion chromatography showed that alpha-hemolysin did not assemble spontaneously even when stored for 1 year. SOS-PAGE analysis revealed that, among the compounds in the crystallizing buffer, MPD could induce heptamer formation. The concentration of MPD that most efficiently induced oligomerization was between 10 and 30%. Based on these observations, we propose MPD as a reagent that can facilitate heptameric pore formation of alpha-hemolysin without membrane binding.
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