ABSTRACT
The nature of the junctions in the lens is controversial. The lens consists of two cell types; its anterior surface is covered by a single layer of cuboidal epithelium, which extends posteriorly to the equator of the lens, while the rest of the mass of the lens is composed of elongated fiber cells. The lens presents numerous technical problems to electrophysiologists studying its intercellular coupling. Reconstitution into planar lipid bilayers provides an alternative for determining the channel-forming properties of membrane proteins. Fortunately, in case of MIP the native lens membranes provide a relatively pure starting material. In addition, HPLC gel filtration allows one to obtain a highly purified protein preparation, consisting of greater than 99% MIP as determined by SDS Polyacrylamide gel electrophoresis. The conductance of BLMs containing MIP channels consistently exhibited a partial decrease in response to voltage ramps.
