title: Selective dye and ionic permeability of gap junction channels formed by connexin45.
abstract: Gap junctions are thought to mediate the direct intercellular coupling of adjacent cells by the gating of an aqueous pore permeable to ions and molecules of up to 1 kD or 8 to 14 A in diameter. We performed ion-substitution and dye-transfer experiments to determine the relative Cl-/K+ conductance and dye permeability of anionic fluorescein derivatives in chick connexin45 (Cx45) channels. We demonstrate that Cx45 forms a 26 +/- 6-picosiemen (pS) channel with a maximum detectable Cl- permeability of 0.2 relative to K+ or Cs+. Although homogeneous channel conductances were observed in multichannel recordings, the open probability estimates were indicative of nonhomogeneous gating behavior and occasional cooperativity. A second conductance state of 19 +/- 4 pS begins to predominate at higher voltages. Cx45 gap junctions are permeable to 2',7'-dichlorofluorescein but are not permeable to the more polar 6-carboxyfluorescein dye. These observations suggest that the Cx45 pore diameter is approximately 10 A and is associated with a fixed negative charge within the junctional channel.
authors.affiliation: Department of Pharmacology, SUNY Health Science Center at Syracuse 13210.
authors.forename: R D
authors.initials: RD
authors.lastname: Veenstra
authors.forename: H Z
authors.initials: HZ
authors.lastname: Wang
authors.forename: E C
authors.initials: EC
authors.lastname: Beyer
authors.forename: P R
authors.initials: PR
authors.lastname: Brink
mesh_terms: D000818:Animals; D002460:Cell Line; D002463:Cell Membrane Permeability; D002645:Chickens; D017630:Connexins / Q000096:biosynthesis / Q000502:physiology*; D004553:Electric Conductivity; D005452:Fluoresceins; D017629:Gap Junctions / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008962:Models, Theoretical; D009447:Neuroblastoma; D011336:Probability; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D017630:Connexins; D005452:Fluoresceins; D007473:Ion Channels; C082920:connexin 45; C024098:6-carboxyfluorescein; C037631:2',7'-dichlorofluorescein