1. Institute for Protein Research, Osaka University, OLABB, 6-2-3, Furuedai, Suita, Osaka 565-0874, Japan
2. Department of Biophysics, Graduate School of Science, Kyoto University, Oiwake, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
3. Picobiology Institute, Graduate School of Life Science, University of Hyogo, Kamigohori, Akoh, Hyogo 678-1297, Japan

Correspondence to: Tomitake Tsukihara^1,3 Correspondence and requests for materials should be addressed to T.T. (Email: tsuki@protein.osaka-u.ac.jp).

Abstract

Gap junctions consist of arrays of intercellular channels between adjacent cells that permit the exchange of ions and small molecules. Here we report the crystal structure of the gap junction channel formed by human connexin 26 (Cx26, also known as GJB2) at 3.5 Å resolution, and discuss structural determinants of solute transport through the channel. The density map showed the two membrane-spanning hemichannels and the arrangement of the four transmembrane helices of the six protomers forming each hemichannel. The hemichannels feature a positively charged cytoplasmic entrance, a funnel, a negatively charged transmembrane pathway, and an extracellular cavity. The pore is narrowed at the funnel, which is formed by the six amino-terminal helices lining the wall of the channel, which thus determines the molecular size restriction at the channel entrance. The structure of the Cx26 gap junction channel also has implications for the gating of the channel by the transjunctional voltage.

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