Fusion of isolated myoblast plasma membranes. An approach to the mechanism.

Fusion of plasma membranes isolated from myoblasts grown in culture has been investigated. 1. Membrane fusion was specifically dependent of Ca2+ at physiological concentrations. However, at higher concentrations of cations, fusion could be triggered not only by Ca2+, but by Mg2+ and Sr2+ as well. 2. The amount of fusion was directly proportional to temperature. 3. Fusion was found to depend on the state of maturation of the myoblast membranes. 4. Experiments with chemically and enzymatically modified membranes and with membranes derived from myoblasts grown in the presence of inhibitors of protein biosynthesis suggest the participation of proteinaceous membrane components in the fusion mechanism.