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 trans-membrane transport processes. Polytopic membrane protein subunits of biological channels are of particular interest. These subunits are specialized membrane proteins that bear 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 have demonstrated that connexins are cotranslationally integrated into the endoplasmic reticulum where they achieve their functional transmembrane topology, and subsequently transported through the Golgi apparatus to reach the plasma membrane. Time-lapse images showed assembly of large gap junction plaques by the fusion of smaller plaques, and that gap junction plaques are not rigid structures, but are extremely dynamic in their appearance and shape. These dynamic live cell images add a new dimension to the classical static picture of gap junctions and provoke a number of interesting questions on their structure and function. Synthesis, assembly and structure of gap junction intercellular channels. Connexin membrane protein biosynthesis is influenced by polypeptide positioning within the translocon and signal peptidase access.