Determinants of slow gating in ClC-0, the voltage-gated chloride channel of Torpedo marmorata

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Item Type:	Article
Title:	Determinants of slow gating in ClC-0, the voltage-gated chloride channel of Torpedo marmorata
Creators Name:	Fong, P., Rehfeldt, A. and Jentsch, T.J.
Abstract:	Membrane hyperpolarization normally activates the slow gate of the Torpedo voltage-gated chloride channel (ClC-0). To elucidate the structural basis of this process, carboxy terminus truncation mutants and chimeras were constructed, expressed in Xenopus oocytes, and evaluated using a two-microelectrode voltage clamp. Introduction of stop codons at several positions between transmembrane domains 12 and 13 (D12 and D13) showed no expression, whereas a truncation just after D13 yielded wild-type currents. A chimera (022) entailing the substitution of the carboxy-terminal cytoplasmic tail after Lys-520 with the corresponding region of ClC-2 lacked slow gating, whereas a more conservative construct (chimera 002), in which D13 was replaced with its ClC-2 analog, retained its capacity to slow gate. These findings suggest that important structures reside within the interdomain stretch (IDS) between D12 and D13. Unlike ClC-2, in which transplantation of "ball" structures could restore gating to constitutively open mutants, transplantation of the ClC-0 IDS to the amino terminus of chimera 022 did not restore gating. Surprisingly, replacement of the IDS by the analogous regions of either ClC-1 or ClC-2 showed slow voltage-activated gating, although the gating was altered. Our findings lead us to conclude that both the functional expression and the slow voltage gating of ClC-0 rely on structures at the carboxy terminus of the channel.
Keywords:	Voltage Clamp, Chimera, Truncation, Animals, Xenopus Laevis
Source:	American Journal of Physiology
ISSN:	0002-9513
Publisher:	American Physiological Society
Volume:	274
Number:	4 Pt 1
Page Range:	C966-C973
Date:	April 1998
Official Publication:	http://ajpcell.physiology.org/cgi/content/abstract/274/4/C966
PubMed:	View item in PubMed

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