Three-Dimensional Structure of a Recombinant Gap Junction Membrane Channel

TLDR

Gap junction membrane channels mediate electrical and metabolic coupling between adjacent cells. Electron crystallography revealed a dodecameric cardiac gap junction channel composed of two hexameric halves, each with 24 α‑helical transmembrane rods, forming a tight extracellular vestibule that seals the channel, at 7.5‑Å resolution in the membrane plane and 21‑Å vertically.

Abstract

Gap junction membrane channels mediate electrical and metabolic coupling between adjacent cells. The structure of a recombinant cardiac gap junction channel was determined by electron crystallography at resolutions of 7.5 angstroms in the membrane plane and 21 angstroms in the vertical direction. The dodecameric channel was formed by the end-to-end docking of two hexamers, each of which displayed 24 rods of density in the membrane interior, which is consistent with an α-helical conformation for the four transmembrane domains of each connexin subunit. The transmembrane α-helical rods contrasted with the double-layered appearance of the extracellular domains. Although not indicative for a particular type of secondary structure, the protein density that formed the extracellular vestibule provided a tight seal to exclude the exchange of substances with the extracellular milieu.