EFFECT OF CALCIUM ION ON S-100, A PROTEIN OF NERVOUS SYSTEM

A specific protein of the nervous system, S-100, appears to exist in multiple forms when subjected to acrylamide gel electrophoresis in the presence of either Ca2+ or 8 m urea, but only in a single form in their absence. Calcium ion causes a limited conformational change in S-100 leading to a more unfolded structure in a region probably containing its single tryptophan, several of its tyrosine and phenylalanine, and two of its three cysteine residues. These effects are not seen with Mg2+. Monovalent cations antagonize the effect of Ca2+, K+ being more effective than Na+. At physiological levels of K+ and Na+ the effects of Ca2+ occur also in its physiological range. © 1969, American Chemical Society. All rights reserved.