Abstract
The oocyte cell/cell‐channel assay was used to identify amino acids involved in the process of cell/cell‐channel formation. The expression of the rat liver gap‐junction protein, connexin 32, in single oocytes, results in the accumulation of a pool of channel precursors. Upon pairing of such oocytes, cell/cell channels form rapidly from this pool. The rate of formation is affected by thiol‐specific reagents and the pH. This suggests the involvement of extracellular cysteine residues in the channel formation process. Two connexin‐32 mutants were generated by site‐directed mutagenesis in which cysteine residues were replaced by serine. Both mutant connexins were unable to form cell/cell channels. Thus, the cysteine residues appear to play an important role in the channel formation process.
