Actomyosin-Like Protein in Brain

Abstract

Two general categories of ATPases are present in tissue. One group requires Na+ and K+ as well as Mg2+ for maximum enzyme activity and functions in active transport of Na + , K + , and other substances across cell membranes. The second group of ATPases requires Mg2+ or Ca2+ for activation. The biochemical and physiological significances of the Mg2+-Ca2 +-activated enzyme systems are less understood. The one major protein system activated by Mg2+ or Ca2+ which has received extensive study is the actomyosin complex; in this system the hydrolysis of ATP stimulated by divalent cations plays an essential role in muscle contraction and relaxation.