title: Structure of alpha-latrotoxin oligomers reveals that divalent cation-dependent tetramers form membrane pores.
abstract: We report here the first three-dimensional structure of alpha-latrotoxin, a black widow spider neurotoxin, which forms membrane pores and stimulates secretion in the presence of divalent cations. We discovered that alpha-latrotoxin exists in two oligomeric forms: it is dimeric in EDTA but forms tetramers in the presence of Ca2+ or Mg2+. The dimer and tetramer structures were determined independently at 18 A and 14 A resolution, respectively, using cryo-electron microscopy and angular reconstitution. The alpha-latrotoxin monomer consists of three domains. The N- and C-terminal domains have been identified using antibodies and atomic fitting. The C4-symmetric tetramers represent the active form of alpha-latrotoxin; they have an axial channel and can insert into lipid bilayers with their hydrophobic base, providing the first model of alpha-latrotoxin pore formation.
authors.affiliation: Biochemistry Department, Imperial College, Exhibition Road, London SW7 2AY, UK.
authors.forename: E V
authors.initials: EV
authors.lastname: Orlova
authors.forename: M A
authors.initials: MA
authors.lastname: Rahman
authors.forename: B
authors.initials: B
authors.lastname: Gowen
authors.forename: K E
authors.initials: KE
authors.lastname: Volynski
authors.forename: A C
authors.initials: AC
authors.lastname: Ashton
authors.forename: C
authors.initials: C
authors.lastname: Manser
authors.forename: M
authors.initials: M
authors.lastname: van Heel
authors.forename: Y A
authors.initials: YA
authors.lastname: Ushkaryov
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001740:Black Widow Spider / Q000737:chemistry*; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D020285:Cryoelectron Microscopy; D019281:Dimerization; D004492:Edetic Acid / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008565:Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009638:Norepinephrine / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D011489:Protein Denaturation; D020673:Protein Renaturation / Q000187:drug effects; D020836:Protein Structure, Quaternary / Q000187:drug effects*; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013111:Spider Venoms / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D002413:Cations, Divalent; D008565:Membrane Proteins; D013111:Spider Venoms; C020763:alpha-latrotoxin; D004492:Edetic Acid; D008274:Magnesium; D002118:Calcium; D009638:Norepinephrine