Electron microscope immunolocation of gap junctions in Drosophila.

Gap junction immunolocation was carried out in thin sections of Lowicryl K4M-embedded Drosophila imaginal wing discs using an affinity-purified polycolonal anti-18kD gap junction protein antibody and a colloidal gold-conjugated secondary antibody. Colloidal gold labelling was predominantly associated with obliquely-sectioned gap junctions, the ends of junctional profiles and other regions in which the adjacent junctional membranes were separated or distorted. The pattern of staining suggests that the determinant recognized by the antibody is relatively inaccessible, probably with a topological location in the transmembrane or extracellular domain of the membrane-spanning connexin protein.