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Ruthenium Red Inhibits the Binding of Calcium to Calmodulin Required for Enzyme Activation

Ruthenium Red Inhibits the Binding of Calcium to Calmodulin Required for Enzyme Activation

T Sasaki, M Naka, F Nakamura, T Tanaka

J Biol Chem. 1992 Oct 25;267(30):21518-23.

PMID: 1383224

Abstract:

The Ca(2+)-calmodulin (CaM)-dependent activation of myosin light chain kinase is inhibited by ruthenium red competitively with respect to Ca2+, with a Ki value of 8.6 microM. The binding of Ca2+ to CaM is inhibited by micromolar concentrations of ruthenium red. In the absence of Ca2+, CaM has two binding sites for ruthenium red with the dissociation constants of 0.36 and 8.7 microM, respectively. Ca2+ antagonizes the binding of ruthenium red to the low-affinity site on CaM. Binding of ruthenium red to the high-affinity site is not affected by Ca2+. The low- and high-affinity sites for ruthenium red are shown to be located in the NH2-terminal half and the COOH-terminal half of CaM, respectively. Lower concentrations of ruthenium red are needed for enzyme inactivation than for the dissociation of enzyme-CaM-Sepharose complex, suggesting these events have different Ca2+ requirements. Moreover, ruthenium red inhibits Ca(2+)-induced contraction of depolarized vascular smooth muscle in a competitive manner with respect to Ca2+. These results suggest that ruthenium red may be a new type of CaM antagonist that inhibits the binding of Ca2+ to CaM and thereby inhibits Ca(2+)-CaM-dependent enzymes and smooth muscle contraction competitively with respect to Ca2+.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP11103723	Ruthenium Red		11103-72-3	Price

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