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KMID : 0613820070170111517
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Journal of Life Science
2007 Volume.17 No. 11 p.1517 ~ p.1522
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Single Channel Analysis of Xenopus Connexin 38 Hemichannel
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Cheon Mi-Saek
Oh Seung-Hoon
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Abstract
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Gap junction channels formed by two adjacent cells allow the passage of small molecules up to ~ 1 kDa between them. Hemichannel (connexon or half of gap junction) also behaves as a membrane channel like sodium or potassium channels in a single cell membrane. Among 26 types of connexin (Cx), Cx32*43E1 (a chimera in which the first extracellular loop of Cx32 has been replaced with that of Cx43), Cx38, Cx46, and Cx50 form functional hemichannels as well as gap junction channels. Although it is known that Xenopus oocytes express endogenous connexin 38 (Cx38), its biophysical characteristics at single channel level are poorly understood. In this study, we performed single channel recordings from single Xenopus oocytes to acquire the biophysical properties of Cx38 including voltage-dependent gating and permeation (conductance and selectivity). The voltage-dependent fast and slow gatings of Cx38 hemichannel are distinct. Fast gating events occur at positive potentials and their open probabilities are low. In contrast, slow gatings dominate at negative potentials with high open probabilites. Based on bi-ionic experiments, Cx38 hemichannel is anion-selective. It will be interesting to test whether charged amino acid residues in the amino terminus of Cx38 are responsible for voltage gatings and permeation.
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KEYWORD
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Gap junction, connexin, hemichannel, voltage gating, selectivity
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