Disulfide bridge reorganization induced by proline mutations in maurotoxin.
Maurotoxin (MTX) is a 34-residue toxin that has been isolated from the venom of the chactidae scorpion Scorpio maurus palmatus, and characterized. Together with Pi1 and HsTx1, MTX belongs to a family of short-chain four-disulfide-bridged scorpion toxins acting on potassium channels. However, contrary to other members of this family, MTX exhibits an uncommon disulfide bridge organization of the type C1-C5, C2-C6, C3-C4 and C7-C8, versus C1-C5, C2-C6, C3-C7 and C4-C8 for both Pi1 and HsTx1. Here, we report that the substitution of MTX proline residues located at positions 12 and/or 20, adjacent to C3 (Cys(13)) and C4 (Cys(19)), results in conventional Pi1- and HsTx1-like arrangement of the half-cystine pairings. In this case, this novel disulfide bridge arrangement is without obvious incidence on the overall three-dimensional structure of the toxin. Pharmacological assays of this structural analog, [A(12),A(20)]MTX, reveal that the blocking activities on Shaker B and rat Kv1.2 channels remain potent whereas the peptide becomes inactive on rat Kv1.3. These data indicate, for the first time, that discrete point mutations in MTX can result in a marked reorganization of the half-cystine pairings, accompanied with a novel pharmacological profile for the analog.
Carlier
E
E
Laboratoire de Neurobiologie des Canaux Ioniques, INSERM U464, IFR Jean Roche, Marseille, France.
Fajloun
Z
Z
Mansuelle
P
P
Fathallah
M
M
Mosbah
A
A
Oughideni
R
R
Sandoz
G
G
Di Luccio
E
E
Geib
S
S
Regaya
I
I
Brocard
J
J
Rochat
H
H
Darbon
H
H
Devaux
C
C
Sabatier
J M
JM
de Waard
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001030:Apamin / Q000378:metabolism; D001667:Binding, Competitive; D004220:Disulfides / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007457:Iodine Radioisotopes; D051663:Kv1.2 Potassium Channel; D051664:Kv1.3 Potassium Channel; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D010455:Peptides / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated; D011392:Proline / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D051381:Rats; D012604:Scorpion Venoms / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D020539:Sequence Analysis, Protein; D051637:Shaker Superfamily of Potassium Channels; D013574:Synaptosomes / Q000378:metabolism; D014981:Xenopus
D004220:Disulfides; D007457:Iodine Radioisotopes; C496972:Kcna2 protein, rat; C496975:Kcna3 protein, rat; D051663:Kv1.2 Potassium Channel; D051664:Kv1.3 Potassium Channel; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012604:Scorpion Venoms; C076413:Shaker B potassium channel polypeptide; D051637:Shaker Superfamily of Potassium Channels; C104498:maurotoxin; D001030:Apamin; D011392:Proline