Gap-junction channels provide a widespread intercellular signalling mechanism. They are constructed of a family of connexin membrane proteins that thread across the membrane four times and oligomerize to generate hexameric gap-junction hemichannels. Using an in vitro cell-free transcription/translation system, we demonstrate that connexin (Cx) 26, one of the smallest connexins, is integrated directly in a post-translational manner into plasma membranes. Protein-cleavage studies of Cx26 integrated into plasma membranes indicate a similar native transmembrane topography to that of Cx26 integrated co-translationally into microsomes. Cx26 integrated post-translationally into plasma membranes oligomerizes and, when incorporated into liposomes, provides permeability to ascorbic acid, suggesting that gap-junction hemichannels are generated. The results provide the basis of a novel alternative mechanism for spontaneous assembly in plasma membranes of Cx26 gap-junction hemichannels that occurs independently of the conventional biogenesis of gap junctions involving connexin trafficking and oligomerization via membrane components of the secretory pathway.
Post-translational integration and oligomerization of connexin 26 in plasma membranes and evidence of formation of membrane pores: implications for the assembly of gap junctions
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Shoeb AHMAD, W. Howard EVANS; Post-translational integration and oligomerization of connexin 26 in plasma membranes and evidence of formation of membrane pores: implications for the assembly of gap junctions. Biochem J 1 August 2002; 365 (3): 693–699. doi: https://doi.org/10.1042/bj20011572
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