help button home button Biophys. J.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wang, C.-T.
Right arrow Articles by Jackson, M. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wang, C.-T.
Right arrow Articles by Jackson, M. B.

Biophys J, August 1999, p. 691-700, Vol. 77, No. 2

Cation Permeability and Cation-Anion Interactions in a Mutant GABA-Gated Chloride Channel from Drosophila

Chih-Tien Wang,* Hai-Guang Zhang,* Thomas A. Rocheleau,§ Richard H. ffrench-Constant,§ and Meyer B. Jackson*

Departments of  *Physiology and  §Entomology, University of Wisconsin-Madison, Madison, Wisconsin 53706 USA

To investigate the structural basis of anion selectivity of Drosophila GABA-gated Cl- channels, the permeation properties of wild-type and mutant channels were studied in Xenopus oocytes. This work focused on asparagine 319, which by homology is one amino acid away from a putative extracellular ring of charge that regulates cation permeation in nicotinic receptors. Mutation of this residue to aspartate reduced channel conductance, and mutation to lysine or arginine increased channel conductance. These results are consistent with an electrostatic interaction between this site and permeating anions. The lysine mutant, but not the arginine mutant, formed a channel that is permeable to cations, and this cannot be explained in terms of electrostatics. The lysine mutant had a 25-mV reversal potential in solutions with symmetrical Cl- and asymmetrical cations. The permeability ratio of K+ to Cl- was determined as 0.33 from reversal potential measurements in KCl gradients. Experiments with large organic cations and anions showed that cation permeation can only be seen in the presence of Cl-, but Cl- permeation can be seen in the absence of permeant cations. Measurements of permeability ratios of organic anions indicated that the lysine mutant has an increased pore size. The cation permeability of the lysine-containing mutant channel cannot be accounted for by a simple electrostatic interaction with permeating ions. It is likely that lysine substitution causes a structural change that extends beyond this one residue to influence the positions of other channel-forming residues. Thus protein conformation plays an important role in enabling ion channels to distinguish between anions and cations.

Biophys J, August 1999, p. 691-700, Vol. 77, No. 2
© 1999 by the Biophysical Society   0006-3495/99/08/691/10  $2.00


This article has been cited by other articles:


Home page
 J. Biol. Chem.Home page
A. K. Bera, M. Chatav, and M. H. Akabas
GABAA Receptor M2-M3 Loop Secondary Structure and Changes in Accessibility during Channel Gating
J. Biol. Chem., November 1, 2002; 277(45): 43002 - 43010.
[Abstract] [Full Text] [PDF]

Home page
 J. Biol. Chem.Home page
M. I. Dibas, E. B. Gonzales, P. Das, C. L. Bell-Horner, and G. H. Dillon
Identification of a Novel Residue within the Second Transmembrane Domain That Confers Use-facilitated Block by Picrotoxin in Glycine alpha 1 Receptors
J. Biol. Chem., March 8, 2002; 277(11): 9112 - 9117.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1999 by the Biophysical Society.