Figure 6.
Replacing the II-III loop of α1C with that of the Musca α1 subunit does not restore tetrad formation. Freeze-fracture electron micrographs of chimera CLM, a cardiac DHPR with the Musca II-III loop sequence, expressed in dysgenic myotubes shows cardiac characteristics (A–C). Clusters of DHPRs (identifiable on basis of their large size) are visible within domed regions of the plasmalemma. Within the clusters, the particle density is fairly high, but the particles show no tendency toward a tetradic grouping (compare with Figures 3, E–F, and 4E for similar failure to restore tetrads by α1C and SkLC).