protein-kinase-inhibitor-peptide-(6-24) and 5--adenylyl-(beta-gamma-methylene)diphosphonate

Free magnesium ions and magnesium-nucleotide complexes can exert opposite effects on many fundamental cellular processes. Although increases in the intracellular concentration of magnesium ions inhibit the L-type calcium current in heart cells, magnesium-adenosine triphosphate complexes (MgATP) would be expected to increase the current by promoting channel phosphorylation. Rapid increases in the intracellular concentration of MgATP induced by flash photolysis of caged magnesium or caged ATP resulted in enhanced calcium current. The increase in calcium current was not prevented by blocking phosphorylation, revealing a previously unrecognized direct regulatory action of the magnesium-nucleotide complex.

Topics: Adenosine Triphosphate; Adenylyl Imidodiphosphate; Animals; Barium; Calcium; Calcium Channels; Carrier Proteins; In Vitro Techniques; Intracellular Signaling Peptides and Proteins; Isoproterenol; Magnesium; Myocardium; Peptide Fragments; Peptides; Phosphorylation; Time Factors