S-100AB INCREASES CA-2+ RELEASE IN PURIFIED SARCOPLASMIC-RETICULUM VESICLES OF FROG SKELETAL-MUSCLE

The S-100ab protein, a mixed isoform member of the S-100 family, stimulates Ca2+-induced Ca2+-release from sarcoplasmic reticulum vesicles purified from frog skeletal muscle cells. The effects of S-100ab appear to be specific and result from its peculiar characteristics rather than the fact that it is a calcium-binding protein. Moreover, the addition of S-100ab to the solution completely abolished the inhibition provoked when Ruthenium Red was added alone. Experiments that added labelled Ryanodine with and without S-100 indicated that the protein diminished the affinity of the alkaloid at its receptor