Functional assembly of gap junction conductance in lipid bilayers: Demonstration that the major 27 kd protein forms the junctional channel

  title={Functional assembly of gap junction conductance in lipid bilayers: Demonstration that the major 27 kd protein forms the junctional channel},
  author={John Ding-E Young and Zanvil Alexander Cohn and Norton B. Gilula},

Voltage dependence of liver gap-junction channels reconstituted into liposomes and incorporated into planar bilayers.

The voltage dependence of rat liver gap junctions was investigated using non-denaturing solubilization and reconstitution of gap-junction protein into proteoliposomes in controlled conditions of connexon aggregation to show that the isolated channel units are highly voltage dependent.

The gap junction: a channel for multiple functions?

This review summarizes the most recent information obtained on the structure of the gap junction by molecular cloning of the major protein components and emphasizes the growing evidence for their functional role in adult tissues formed by highly differentiated secretory cells.

Reconstitution of channels from preparations enriched in lens gap junction protein MP70

Detergent-solubilized ovine lens membrane proteins, enriched in the 70-kDa gap junction component (MP70), were reconstituted into planar lipid bilayers and analyzed for channel activities, finding one channel was asymmetrically voltage dependent and its properties would be consistent with the expected properties of junctional hemichannels.

Structure-activity relations of the cardiac gap junction channel.

Biophysics of gap junctions.

Physical Characterization of Gap Junction Membrane Connexons (Hemi-channels) Isolated from Rat Liver (*)

Analysis of enriched subcellular fractions of double membrane gap junctions from rat livers indicate that the isolated complex (connexon) principally contains a hexameric arrangement of gap junction protein to form a single membrane hemi-channel.

Biochemical and biophysical analysis of cell-to-cell channels and regulation of gap junctional permeability.

Correlative studies on the molecular and cellular level should help to clarify the physiological meaning of intercellular communication by gap junctions.



Measurement of single channel currents from cardiac gap junctions.

By monitoring whole-cell currents in pairs of embryonic heart cells with two independent patch-clamp circuits, the properties of single gap junction channels have been investigated andChannel activity and macroscopic junctional conductance were both decreased by the uncoupling agent 1-octanol.

Isolated liver gap junctions: gating of transjunctional currents is similar to that in intact pairs of rat hepatocytes.

Currents from isolated liver gap junctions are recorded using patch electrodes dipped through a layer of mixed lipids whose concentrations match those of isolated liver appositional membranes, and their block by low pH and other agents indicates that the gating mechanisms are intrinsic to the gap junction junctions themselves and presumably result from conformational change in the channel-forming protein.

Purified lens junctional protein forms channels in planar lipid films.

It is most likely that the reconstituted channels are formed by MIP-26, the major protein component of the isolated lens junctions, which are likely to account for the electrical coupling observed between intact lens fibers.

Rat liver gap junction protein: properties and partial sequence.

The polypeptide characteristic of trypsin-treated gap junction preparations is shown to be two distinctpolypeptides, both derived from the Mr 28,000 protein.

The Nature of the Negative Resistance in Bimolecular Lipid Membranes Containing Excitability-Inducing Material

It is concluded that the EIM-doped bilayer contains ion-conducting channels capable of undergoing transitions between two states of different conductance, which explains the negative resistance observed for bimolecular lipid membranes treated with greater amounts of EIM.

Electrophysiological properties of gap junctions between dissociated pairs of rat hepatocytes

Physiological properties of isolated pairs of rat hepatocytes were examined within 5 h after dissociation, finding the low apparent pK and very steep pHi-gj relation of the liver gap junction contrast with higher pKs and more gradually rising curves in other tissues.

Gap junctional conductance is a simple and sensitive function of intracellular pH.

The closure of gap junction channels at low pHi appears to be a cooperative process involving several charged sites and implies that protons act directly on the channel macromolecules and not through an intermediate in the cytoplasm.

Formation of bimolecular membranes from lipid monolayers and a study of their electrical properties.

  • M. MontalP. Mueller
  • Chemistry
    Proceedings of the National Academy of Sciences of the United States of America
  • 1972
There is a significant difference between the capacity of bilayers made from mono-layers and that of hydrocarbon-containing bilayer made by phase transition; the average values are 0.9 and 0.45 muF cm(-2), respectively, which approximates that of biological membranes.

Isolation and characterization of gap junctions from rat liver.