S‐100a0 protein stimulates Ca2+ ‐induced Ca2+ release from isolated sarcoplasmic reticulum vesicles

Abstract
S‐100a0 protein, the αα‐isoform of the S‐100 family, stimulates Ca2+ ‐induced Ca2+ release from terminal cisternae isolated from rat skeletal muscle cells. The stimulatory effect of S‐100a0 is maximal at ∼5 μM S‐100a0 and half maximal at ∼0.1 μM S‐100a0, at 1.8 μM free Ca2+ in the presence of 5 mM Mg2+ plus 0.1 M KCl. The effect of the protein on Ca2+ ‐induced Ca2+ release is completely inhibted by the calcium release blocker, ruthenium red.