The GXGXG motif in the pI(Cln) protein is not important for the nucleotide sensitivity of the pI(Cln)-induced Cl- current in Xenopus oocytes.
It has been proposed that the pI(Cln) protein forms a nucleotide-sensitive plasma membrane anion channel with a GXGXG motif being an essential component of the extracellular nucleotide-binding site. To evaluate this hypothesis, we have performed voltage-clamp experiments on Xenopus laevis oocytes injected with RNA encoding a rat mutant pI(Cln) in which the three glycines of the putative nucleotide-binding site have been changed into alanines (G54A; G56A; G58A). The injected oocytes displayed outwardly rectifying anion currents, which were voltage-dependently blocked by extracellular cAMP, but which were not affected by removal of extracellular Ca2+. Furthermore, the mutation did not affect the voltage-dependent inactivation. We therefore conclude that there is no evidence in favour of an extracellular nucleotide-binding site in pI(Cln).
Voets
T
T
Katholieke Universiteit Leuven, Laboratorium voor Fysiologie Campus Gasthuisberg O and N, Belgium.
Buyse
G
G
Droogmans
G
G
Eggermont
J
J
Nilius
B
B
D000818:Animals; D002118:Calcium / Q000502:physiology; D018118:Chloride Channels / Q000737:chemistry* / Q000502:physiology; D000242:Cyclic AMP / Q000494:pharmacology; D004553:Electric Conductivity; D005110:Extracellular Space; D015640:Ion Channel Gating; D007473:Ion Channels; D008564:Membrane Potentials; D016297:Mutagenesis, Site-Directed; D009865:Oocytes; D051381:Rats; D013329:Structure-Activity Relationship; D029867:Xenopus Proteins; D014982:Xenopus laevis
C498731:CLNS1A protein, Xenopus; D018118:Chloride Channels; C498729:Clns1a protein, rat; D007473:Ion Channels; D029867:Xenopus Proteins; D000242:Cyclic AMP; D002118:Calcium