Interaction between tetraethylammonium and amino acid residues in the pore of cloned voltage-dependent potassium channels

Michael P. Kavanaugh, Michael D. Varnum, Peregrine B. Osborne, MacDonald J. Christie, Andreas E. Busch, John Adelman, R. Alan North

Research output: Contribution to journalArticle

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Abstract

Extracellular tetraethylammonium (TEA) inhibits currents in Xenopus oocytes that have been injected with mRNAs encoding voltage-dependent potassium channels. Concentration-response curves were used to measure the affinity of TEA; this differed up to 700-fold among channels RBK1 (KD 0.3 mM), RGK5 (KD 11 mM), and RBK2 (KD > 200 mM). Studies in which chimeric channels were expressed localized TEA binding to the putative extracellular loop between transmembrane domains S5 and S6. Site-directed mutagenesis of residues in this region identified the residue Tyr379 of RBK1 as a crucial determinant of TEA sensitivity; substitution of Tyr in the equivalent positions of RBK2 (Val381) and RGK5 (His401) made these channels as sensitive to TEA as RBK1. Nonionic forces are involved in TEA binding because (i) substitution of the Phe for Tyr379 in RBK1 increased its affinity, (ii) protonation of His401 in RGK5 selectively reduced its affinity, and (iii) the affinity of TEA was unaffected by changes in ionic strength. The results suggest an explanation for the marked differences in TEA sensitivity that have been observed among naturally occurring and cloned potassium channels and indicate that the amino acid corresponding to residue 379 in RBK1 lies within the external mouth of the ion channel.

Original languageEnglish (US)
Pages (from-to)7583-7587
Number of pages5
JournalJournal of Biological Chemistry
Volume266
Issue number12
StatePublished - Apr 25 1991

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Tetraethylammonium
Potassium Channels
Amino Acids
Electric potential
Substitution reactions
S 6
Mutagenesis
Protonation
Xenopus
Site-Directed Mutagenesis
Ionic strength
Ion Channels
Osmolar Concentration
Oocytes
Mouth
Messenger RNA

ASJC Scopus subject areas

  • Biochemistry

Cite this

Kavanaugh, M. P., Varnum, M. D., Osborne, P. B., Christie, M. J., Busch, A. E., Adelman, J., & North, R. A. (1991). Interaction between tetraethylammonium and amino acid residues in the pore of cloned voltage-dependent potassium channels. Journal of Biological Chemistry, 266(12), 7583-7587.

Interaction between tetraethylammonium and amino acid residues in the pore of cloned voltage-dependent potassium channels. / Kavanaugh, Michael P.; Varnum, Michael D.; Osborne, Peregrine B.; Christie, MacDonald J.; Busch, Andreas E.; Adelman, John; North, R. Alan.

In: Journal of Biological Chemistry, Vol. 266, No. 12, 25.04.1991, p. 7583-7587.

Research output: Contribution to journalArticle

Kavanaugh, MP, Varnum, MD, Osborne, PB, Christie, MJ, Busch, AE, Adelman, J & North, RA 1991, 'Interaction between tetraethylammonium and amino acid residues in the pore of cloned voltage-dependent potassium channels', Journal of Biological Chemistry, vol. 266, no. 12, pp. 7583-7587.
Kavanaugh MP, Varnum MD, Osborne PB, Christie MJ, Busch AE, Adelman J et al. Interaction between tetraethylammonium and amino acid residues in the pore of cloned voltage-dependent potassium channels. Journal of Biological Chemistry. 1991 Apr 25;266(12):7583-7587.
Kavanaugh, Michael P. ; Varnum, Michael D. ; Osborne, Peregrine B. ; Christie, MacDonald J. ; Busch, Andreas E. ; Adelman, John ; North, R. Alan. / Interaction between tetraethylammonium and amino acid residues in the pore of cloned voltage-dependent potassium channels. In: Journal of Biological Chemistry. 1991 ; Vol. 266, No. 12. pp. 7583-7587.
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