title: Increasing the molecular contacts between maurotoxin and Kv1.2 channel augments ligand affinity.
abstract: Scorpion toxins interact with their target ion channels through multiple molecular contacts. Because a "gain of function" approach has never been described to evaluate the importance of the molecular contacts in defining toxin affinity, we experimentally examined whether increasing the molecular contacts between a toxin and an ion channel directly impacts toxin affinity. For this purpose, we focused on two scorpion peptides, the well-characterized maurotoxin with its variant Pi1-like disulfide bridging (MTX(Pi1)), used as a molecular template, and butantoxin (BuTX), used as an N-terminal domain provider. BuTX is found to be 60-fold less potent than MTX(Pi1) in blocking Kv1.2 (IC(50) values of 165 nM for BuTX versus 2.8 nM for MTX(Pi1)). Removal of its N-terminal domain (nine residues) further decreases BuTX affinity for Kv1.2 by 5.6-fold, which is in agreement with docking simulation data showing the importance of this domain in BuTX-Kv1.2 interaction. Transfer of the BuTX N-terminal domain to MTX(Pi1) results in a chimera with five disulfide bridges (BuTX-MTX(Pi1)) that exhibits 22-fold greater affinity for Kv1.2 than MTX(Pi1) itself, in spite of the lower affinity of BuTX as compared to MTX(Pi1). Docking experiments performed with the 3-D structure of BuTX-MTX(Pi1) in solution, as solved by (1)H-NMR, reveal that the N-terminal domain of BuTX participates in the increased affinity for Kv1.2 through additional molecular contacts. Altogether, the data indicate that acting on molecular contacts between a toxin and a channel is an efficient strategy to modulate toxin affinity.
authors.affiliation: Laboratoire d'Ingénierie des Protéines, CNRS FRE 2738, IFR Jean Roche, Faculté de Médecine Nord, Marseille, France.
authors.forename: Sarrah
authors.initials: S
authors.lastname: M'Barek
authors.forename: Benjamin
authors.initials: B
authors.lastname: Chagot
authors.forename: Nicolas
authors.initials: N
authors.lastname: Andreotti
authors.forename: Violeta
authors.initials: V
authors.lastname: Visan
authors.forename: Pascal
authors.initials: P
authors.lastname: Mansuelle
authors.forename: Stephan
authors.initials: S
authors.lastname: Grissmer
authors.forename: Mohamed
authors.initials: M
authors.lastname: Marrakchi
authors.forename: Mohamed
authors.initials: M
authors.lastname: El Ayeb
authors.forename: François
authors.initials: F
authors.lastname: Sampieri
authors.forename: Hervé
authors.initials: H
authors.lastname: Darbon
authors.forename: Ziad
authors.initials: Z
authors.lastname: Fajloun
authors.forename: Michel
authors.initials: M
authors.lastname: De Waard
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Sabatier
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D019295:Computational Biology / Q000379:methods*; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D004594:Electrophysiology; D020128:Inhibitory Concentration 50; D051663:Kv1.2 Potassium Channel / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods*; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012604:Scorpion Venoms / Q000737:chemistry*; D012605:Scorpions; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014269:Trifluoroacetic Acid / Q000737:chemistry
chemical_list: D004220:Disulfides; D051663:Kv1.2 Potassium Channel; D010455:Peptides; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins; D012604:Scorpion Venoms; C411251:butantoxin; C104498:maurotoxin; D014269:Trifluoroacetic Acid; D003545:Cysteine