ASSEMBLY OF CONNEXINS AND MP26 IN LENS FIBER PLASMA-MEMBRANES STUDIEDBY SDS-FRACTURE IMMUNOLABELING

The SDS-fracture immunolabeling technique, unlike conventional freeze- fracture, provides direct evidence for the biochemical nature of membr ane constituents. SDS-fracture immunolabeling shows that during differ entiation of lens fiber cells the onset of junctional assembly is char acterized by the presence of small clusters and linear arrays comprisi ng connexins alpha 3 and alpha 8, At this initial stage MP26, a major fiber membrane constituent, appears to be colocalized with these two c onnexins, The application of double-immunogold labeling reveals that w hen large junctional plaques are assembled MP26 becomes mainly associa ted with the periphery of the junctional domains. This type of distrib ution suggests that MP26 may play a role in the clustering and gatheri ng of connexons, In aged nuclear fiber membranes connexins, MP26 and t heir proteolytic derivatives form an orthogonal lattice of repeating s ubunits.