title: GroEL protects the sarcoplasmic reticulum Ca(++)-dependent ATPase from inactivation in vitro.
abstract: The molecular chaperone, GroEL, facilitates correct protein folding and inhibits protein aggregation. The function of GroEL is often, though not invariably, dependent on the co-chaperone, GroES, and ATP. In this study it is shown that GroEL alone substantially reduces the inactivation of purified Ca(++)-ATPase from rabbit skeletal muscle sarcoplasmic reticulum. In the absence of GroEL, the enzyme became completely inactive in about 45-60 hours when kept at 25 degrees C, while in the presence of an equimolar amount of GroEL, the enzyme remained approximately 80% active even after 75 hours. Equimolar amounts of BSA or lysozyme were unable to protect the enzyme from inactivation under identical conditions. Analysis by SDS-PAGE showed GroEL was acting by blocking the aggregation of ATPase at 25 degrees C. GroEL was not as effective in protection at -20 degrees C or 4 degrees C. These results are discussed in the context of current models of the GroEL mechanism.
mesh_terms: D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D018834:Chaperonin 60 / Q000378:metabolism*; D004789:Enzyme Activation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*