Voltage-sensitive gating induced by a mutation in the fifth transmembrane domain of CFTR.
A mutation in the fifth transmembrane domain of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel (V317E) resulted in whole cell currents that exhibited marked outward rectification on expression in Xenopus oocytes. However, the single-channel unitary current (i)-voltage (V) relationship failed to account for the rectification of whole cell currents. In excised patches containing one to a few channels, the time-averaged single-channel current (I)-V relationship (I = N x P(o) x i, where N is the number of active channels and P(o) is open probability) of V317E CFTR displayed outward rectification, whereas that of wild-type CFTR was linear, indicating that the P(o) of V317E CFTR is voltage dependent. The decrease in P(o) at negative potentials was due to both a decreased burst duration and a decreased opening rate that could not be ameliorated by a 10-fold increase in ATP concentration. This behavior appears to reflect a true voltage dependence of the gating process because the P(o)-V relationship did not depend on the direction of Cl(-) movement. The results are consistent with the introduction, by a point mutation, of a novel voltage-dependent gating mode that may provide a useful tool for probing the portions of the protein that move in response to ATP-dependent gating.
Zhang
Zhi-Ren
ZR
Center for Cell and Molecular Signaling, Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Zeltwanger
Shawn
S
Smith
Stephen S
SS
Dawson
David C
DC
McCarty
Nael A
NA
D000818:Animals; D002712:Chlorides / Q000008:administration & dosage / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D006706:Homeostasis; D015640:Ion Channel Gating / Q000502:physiology*; D009154:Mutation / Q000502:physiology*; D009865:Oocytes / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics; D012996:Solutions; D014981:Xenopus
D002712:Chlorides; D012996:Solutions; D019005:Cystic Fibrosis Transmembrane Conductance Regulator