title: Molecular basis of the mammalian potency of the scorpion alpha-like toxin, BmK M1.
abstract: In-depth structure-function studies of voltage-gated Na+ channels and peptide toxins are continuously increasing our understanding of their interaction. In this study, an effective yeast expression system was used to study the role of 14 N- and C-terminal residues from the alpha-like toxin BmK M1 from the Chinese scorpion Buthus martensii Karsch. With the use of site-directed mutagenesis, all of these residues were individually substituted by one or more amino acids, resulting in a total of 19 mutants. These were then subjected to a bioassay on mice, an elaborate electrophysiological characterization on three cloned voltage-gated Na+ channels (Nav1.2, Nav1.5, and para), and a circular dichroism analysis. Our results reveal large mutant-dependent differences that emphasize important and specific roles for the studied residues. By mutating single amino acids, we were able to redirect the alpha-like characteristics of BmK M1 (active on both mammals and insects) to either much higher mammal specificity or, in a few cases, total insect specificity. This study therefore represents a thorough mapping and elucidation of three epitopes that underlie the molecular basis of the mammalian and insecticidal potency of the scorpion alpha-like toxin, BmK M1 on voltage-gated Na+ channels.
authors.affiliation: Center for Molecular Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Li-Hui
authors.initials: LH
authors.lastname: Liu
authors.forename: Frank
authors.initials: F
authors.lastname: Bosmans
authors.forename: Chantal
authors.initials: C
authors.lastname: Maertens
authors.forename: Ron-Han
authors.initials: RH
authors.lastname: Zhu
authors.forename: Da-Cheng
authors.initials: DC
authors.lastname: Wang
authors.forename: Jan
authors.initials: J
authors.lastname: Tytgat
mesh_terms: D000818:Animals; D002942:Circular Dichroism; D004594:Electrophysiology; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D015870:Gene Expression; D019476:Insect Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D007313:Insecta / Q000502:physiology; D007306:Insecticides; D051379:Mice; D008813:Mice, Inbred ICR; D009132:Muscles / Q000187:drug effects / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009865:Oocytes / Q000378:metabolism; D017354:Point Mutation; D011487:Protein Conformation; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012604:Scorpion Venoms / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013131:Spine; D013329:Structure-Activity Relationship; D014162:Transfection; D014982:Xenopus laevis
chemical_list: C403888:BmK M1 neurotoxin; D019476:Insect Proteins; D007306:Insecticides; D011994:Recombinant Proteins; D012604:Scorpion Venoms; D015222:Sodium Channels