State-dependent inhibition of cystic fibrosis transmembrane conductance regulator chloride channels by a novel peptide toxin.
Peptide toxins from animal venom have been used for many years for the identification and study of cation-permeable ion channels. However, no peptide toxins have been identified that interact with known anion-selective channels, including cystic fibrosis transmembrane conductance regulator (CFTR), the protein defective in cystic fibrosis and a member of the ABC transporter superfamily. Here, we describe the identification and initial characterization of a novel 3.7-kDa peptide toxin, GaTx1, which is a potent and reversible inhibitor of CFTR, acting from the cytoplasmic side of the membrane. Thus, GaTx1 is the first peptide toxin identified that inhibits a chloride channel of known molecular identity. GaTx1 exhibited high specificity, showing no effect on a panel of nine transport proteins, including Cl(-) and K(+) channels, and ABC transporters. GaTx1-mediated inhibition of CFTR channel activity is strongly state-dependent; both potency and efficacy are reduced under conditions of elevated [ATP], suggesting that GaTx1 may function as a non-competitive inhibitor of ATP-dependent channel gating. This tool will allow the application of new quantitative approaches to study CFTR structure and function, particularly with respect to the conformational changes that underlie transitions between open and closed states.
Fuller
Matthew D
MD
Program in Molecular and Systems Pharmacology, Emory University, Atlanta, GA 30322, USA.
Thompson
Christopher H
CH
Zhang
Zhi-Ren
ZR
Freeman
Cody S
CS
Schay
Eszter
E
Szakács
Gergely
G
Bakos
Eva
E
Sarkadi
Balázs
B
McMaster
Denis
D
French
Robert J
RJ
Pohl
Jan
J
Kubanek
Julia
J
McCarty
Nael A
NA
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D018118:Chloride Channels / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry / Q000502:physiology*; D004594:Electrophysiology / Q000379:methods; D006801:Humans; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012604:Scorpion Venoms / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis / Q000378:metabolism
C505032:CFTR protein, human; D018118:Chloride Channels; C526915:GaTx1 protein, Leiurus quinquestriatus hebraeus; D012604:Scorpion Venoms; D019005:Cystic Fibrosis Transmembrane Conductance Regulator