Splitting, junctional membranes

Interactions between Hemichannels. What does the isolation of single hemichannels imply about the end-to-end interactions of hemichannels This is an important consideration for possible reconstitution of junctional channels from individual hemichannels. Unfortunately, the data summarized above are not informative on this point. Harsh conditions are required to split apart isolated junctional membranes (7, 79). However, any junctional structures that were easily solubilized, as in the affinity-purified preparation, would not have been recovered as isolated junctional membranes and so might not require such harsh conditions for splitting. 

The starting material for the affinity purification was predominantly plasma membrane from presumably well-coupled cells therefore, the con-nexin that is isolated is most likely from junctional structures. Because the purified connexin-32 is predominantly in structures the size of single hemichannels, a simple conclusion is that octylglucoside can disrupt the end-to-end interactions of junctional channels. However, there is the caveat that the junctions may split prior to solubilization, that is, in the preparation of the crude plasma membrane fraction. Junctions can split when a tissue is perfused with hyperosmotic solutions (II7), so a cellular splitting could precede disruption of junctional channels by octylglucoside. 

A schematic illustration of the function and structure of a BPM. The right-hand side illustrates the alternatives of salt ions separation or water-splitting reaction at the BPM junction region. (Reprinted from Desalination 90, H. Strathmann, Theoretical and practical aspects of preparing bipolar membranes, 1993,303-323. Copyright 1993, with permission from Elsevier.)... 

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