1. The effect of divalent metal ions on the ATPase activity and ADP binding of H-meromyosin
- Author
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L. Marchioli, Anthony Martonosi, and Mazhar N. Malik
- Subjects
Electrophoresis ,inorganic chemicals ,Cations, Divalent ,Uracil Nucleotides ,Inorganic chemistry ,Biophysics ,Muscle Proteins ,Cytosine Nucleotides ,Myosins ,Binding, Competitive ,Biochemistry ,Dissociation (chemistry) ,Metal ,ATP hydrolysis ,Magnesium ,Inosine Nucleotides ,Molecular Biology ,Equilibrium constant ,Adenosine Triphosphatases ,Binding Sites ,biology ,Chemistry ,Muscles ,Myosin Subfragments ,Active site ,Adenosine Diphosphate ,Enzyme Activation ,Dissociation constant ,Kinetics ,Crystallography ,Metals ,visual_art ,visual_art.visual_art_medium ,biology.protein ,ADP binding ,Spectrophotometry, Ultraviolet ,Dialysis ,Nucleoside ,Protein Binding - Abstract
The effects of Mg2+, Mn2+, Zn2+, Co2+, Ni2+, Ca2+, and Sr2+ upon the equilibrium constant (K) and formation rate constant (k1) of H-meromyosin-ADP complex were studied. The affinity constant of ADP binding decreases in the following order Mn > Mg > Zn > Ni > Co > Sr ∼- Ca. The calculated dissociation rate constant (k2) of the enzyme-ADP complex was similar to the rate of ATP hydrolysis with all divalent metals tested, except Sr2+. With Mg as predominant metal ion the following dissociation constants were obtained for the binding of various nucleoside diphosphates to H-meromyosin: ADP 1–2 × 10−6 m , UDP 2 × 10−5 m , CDP 3 × 10−5 m , IDP 10−4 m . The results are compatible with the suggestion that at 6 °C the dissociation of ADP from the active site limits the rate of ATP hydrolysis with Mg2+, Mn2+, Co2+, and Ca2+.
- Published
- 1972
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