Effect of S-100 protein on microtubule assembly-disassembly

S-100 protein was examined for its ability to affect microtubule assembly-disassembly in vitro. Addition of S-100 protein inhibited microtubule assembly in a dose-dependent manner in the presence of Ca2+, but this effect was not observed in the presence of 2 mM EGTA. The interaction of microtubule proteins with S-100 protein was also demonstrated by Ca+-dependent affinity chromatography on S-100 protein-Sepharose. The proteins bound to the Sepharose column comigrated with tubulin as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results might suggest a possible physiological role of S-100 protein in the microtubule assembly-disassembly system.