SPECTRAL STUDIES ON THE CALCIUM-BINDING PROPERTIES OF MTS1 PROTEIN AND ITS INTERACTION WITH TARGET PROTEIN

Two calcium-binding sites of the Mts1 protein, a member of S-100 prote in family, were distinguished with the Fluo-3 fluorescent technique, T he geometric mean of the apparent dissociation constant (K-d) for thes e two sites is 2.6 mu M; the Hill coefficient (n(H)) is 0.98, In the p resence of a novel target protein p37, isolated from the mouse adenoca rcinoma cell line CSML-100, Mts1 binds Ca2+ ions with higher affinity and with strong positive cooperativity (K-d=0.2 mu M, n(H)=1.91). Inte raction of Mts1 with p37 is confirmed by the fluorescent probe 2-p-tol uidinylnaphthalene-6-sulfonate (TNS), Reaction with TNS shows that p37 interacts with the hydrophobic site of Mts1 which is exposed due to t he binding of Ca2+ ions. (C) 1997 Federation of European Biochemical S ocieties.