The membrane lipids, however, form a tight seal and prevent simple exchange of biological molecules. We are interested in understanding what role membrane proteins might play in transmembrane transport processes. Polytopic membrane protein subunits of biological channels are of particular interest. These subunits are specialized membrane proteins that have charged amino acid residues within the transmembrane domains to allow formation of hydrophilic pores within the lipid bilayer. Oligomeric gap junctions are an example of such biological channels.
Some untypical features associated with their unique function are extremely interesting.
We showed that connexins are cotranslationally integrated into the endoplasmic reticulum, where they achieve their functional transmembrane topology, and subsequently are transported through the Golgi apparatus to reach the plasma membrane. Time-lapse images showed that large gap junction plaques are formed by the fusion of smaller plaques and that gap junction plaques are not rigid structures but are extremely dynamic in appearance and shape. These dynamic images of live cells add a new dimension to the classical static picture of gap junctions and provoke a number of interesting questions about the structure and function of the junctions. Methods, in press.