Ca2+/S100 regulation of giant protein kinases

Ca2+/S100A1(sub 2) is a Ca2+ -binding protein that activates the myosin-associated giant protein kinase twitchin with a high specificity. The S100A1(sub 2)-binding region of twitchin is present in the autoregulatory sequence that is involved in the intrasteric autoinhibition of twitchin. The activation of twitchin is Ca2+ dependent and increases in the presence of low amounts of Zn2+. S100A1(sub 2) is a possible activator of the entire family of giant protein kinases that participate in muscle contraction and cytoskeletal structure.