Intracellular signaling through long-range linked functions in the Ca2+ transport ATPase.

The Ca2+ transport ATPases of intracellular membranes exhibit an intracellular long-range functional linkage which is the basic mechanistic device for Ca2+ transport through ATP utilization. The functional linkage operates between a phosphorylation (catalytic) domain located in the extramembranous region, and a Ca2+ binding domain located in the membrane bound region of the enzyme. The two domains are separated by a distance of approximate to 50 Angstrom, and are both affected by binding of a single molecule of the highly specific inhibitor, thapsigargin, to the enzyme. Functional and structural features are here described to explain the long-range linkage through the protein structure.