Roles of K149, G352, and H401 in the channel functions of ClC-0: Testing the predictions from theoretical calculations

Xiao Dong Zhang, Yong Li, Wei Ping Yu, Tsung-Yu Chen

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The ClC family of Cl- channels and transporters comprises membrane proteins ubiquitously present in species ranging from prokaryotes to mammals. The recently solved structures of the bacterial ClC proteins have provided a good model to guide the functional experiments for the eukaryotic Cl- channels. Theoretical calculations based on the bacterial ClC structures have identified several residues critical for the Cl- binding energy in the Cl- transport pathway. It was speculated that the corresponding residues in eukaryotic Cl- channels might play similar roles for the channel functions. In this study, we made a series of mutations in three such residues in eukaryotic ClC Cl- channels (K149, G352, and H401 in ClC-0) and studied the functional consequences on the channel properties. A cysteine modification approach was also employed to evaluate the electrostatic effects of the charge placed at these three positions. The experimental results revealed that among the three residues tested, K149 plays the most important role in controlling both the gating and the permeation functions of ClC-0. On the other hand, mutations of H401 alter the channel conductance but not the gating properties, while mutations of G352 result in very little functional consequence. The mutation of K149 into a neutral residue leucine (K149L) shifts the activation curve and leads to flickery channel openings. The anion permeability ratios derived from bi-ionic experiments are also significantly altered in that the selectivity of Cl - over other anions is decreased. Furthermore, removing the positive charge at this position reduces and increases, respectively, the accessibility of the negatively and positively charged methane thiosulfonate reagents to the pore. The control of the accessibility to charged MTS reagents and the regulation of the anion permeation support the idea that K149 exerts an electrostatic effect on the channel function, confirming the prediction from computational studies.

Original languageEnglish (US)
Pages (from-to)435-447
Number of pages13
JournalJournal of General Physiology
Volume127
Issue number4
DOIs
StatePublished - Apr 2006

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Anions
Mutation
Static Electricity
Bacterial Structures
Bacterial Proteins
Leucine
Cysteine
Mammals
Permeability
Membrane Proteins
methanethiosulfonate

ASJC Scopus subject areas

  • Physiology

Cite this

Roles of K149, G352, and H401 in the channel functions of ClC-0 : Testing the predictions from theoretical calculations. / Zhang, Xiao Dong; Li, Yong; Yu, Wei Ping; Chen, Tsung-Yu.

In: Journal of General Physiology, Vol. 127, No. 4, 04.2006, p. 435-447.

Research output: Contribution to journalArticle

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abstract = "The ClC family of Cl- channels and transporters comprises membrane proteins ubiquitously present in species ranging from prokaryotes to mammals. The recently solved structures of the bacterial ClC proteins have provided a good model to guide the functional experiments for the eukaryotic Cl- channels. Theoretical calculations based on the bacterial ClC structures have identified several residues critical for the Cl- binding energy in the Cl- transport pathway. It was speculated that the corresponding residues in eukaryotic Cl- channels might play similar roles for the channel functions. In this study, we made a series of mutations in three such residues in eukaryotic ClC Cl- channels (K149, G352, and H401 in ClC-0) and studied the functional consequences on the channel properties. A cysteine modification approach was also employed to evaluate the electrostatic effects of the charge placed at these three positions. The experimental results revealed that among the three residues tested, K149 plays the most important role in controlling both the gating and the permeation functions of ClC-0. On the other hand, mutations of H401 alter the channel conductance but not the gating properties, while mutations of G352 result in very little functional consequence. The mutation of K149 into a neutral residue leucine (K149L) shifts the activation curve and leads to flickery channel openings. The anion permeability ratios derived from bi-ionic experiments are also significantly altered in that the selectivity of Cl - over other anions is decreased. Furthermore, removing the positive charge at this position reduces and increases, respectively, the accessibility of the negatively and positively charged methane thiosulfonate reagents to the pore. The control of the accessibility to charged MTS reagents and the regulation of the anion permeation support the idea that K149 exerts an electrostatic effect on the channel function, confirming the prediction from computational studies.",
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