ABSTRACT
The 40-50-fold increase in the Ca2+-ATPase content of sarcoplasmic reticulum during muscle development is accompanied by an expansion of the surface area of the phospholipid bilayer and by coordinated synthesis and insertion of other SR/ER proteins (Martonosi, 1982; Martonosi et al., 1980, 1982, 1987). All these components of sarcoplasmic reticulum must be present at defined concentration in relationship to the myofibrils and other cellular structures to assure that the Ca2+ fluxes during muscle activation are commensurate with the desired level of muscle activity. The mechanisms of this matching are largely unknown, but protein degradation plays an obvious role in the process. In this chapter the proteolytic degradation pathways of sarcoplasmic reticulum are outlined that regulate the turnover of Ca2+-ATPase and other SR proteins.
