The binding of divalent cations to myosin.
Centrifuge transport, equilibrium dialysis, and electron paramagnetic resonance studies on the binding of Mn2+ to myosin revealed two sets of noninteracting binding sites which are characterized at low ionic strength (0.016 M KCl) by affinity constants of 10(6) M-1 (Class I) and 10(3) M-1 (Class II), respectively. At 0.6 M KCl concentration, the affinity of Mn2+ for both sets of sites is reduced. The maximum number of binding sites is 2 for the high affinity and 20 to 25 for the low affinity set. Other divalent metal ions displace Mn2+ from the high affinity sites in the following order of effectiveness: Ca greater than Mg = Zn = Co greater than Sr greater than Ni. The inhibitory effects of Mg2+ and Ca2+ upon the Mn2+ binding are competitive with inhibitor constants of 0.75 to 1 mM which is similar to that of the low affinity divalent metal ion binding sites. Exposure of myosin to 37 degrees partially inhibits Mn2+ binding to Class I parallel with inhibition of ATPase activity. The binding of Mn2+ to the high affinity binding sites is not significantly influenced by ADP or PPi, although Mn2+ increases the affinity of ADP binding to myosin at high ionic strength.
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium; D002413:Cations, Divalent; D003035:Cobalt; D007700:Kinetics; D008274:Magnesium; D008345:Manganese; D009218:Myosins / Q000378:metabolism; D009532:Nickel; D011485:Protein Binding; D011817:Rabbits; D013324:Strontium; D015032:Zinc
D002413:Cations, Divalent; D003035:Cobalt; D008345:Manganese; D009532:Nickel; D009218:Myosins; D008274:Magnesium; D015032:Zinc; D002118:Calcium; D013324:Strontium