Figure 3. Energy landscape of the Mg²⁺-sensitive states of myosin-5b.

Illustrated are the relative changes in enthalpy (ΔH₁ ^‡, ΔH₂ ^‡, ΔH_Mg) of the reaction according to the proposed kinetic model. The enthalpic barriers ΔH₁ ^‡ and ΔH₂ ^‡ correspond to the two alternative Mg²⁺-ADP and ADP dissociation pathways, respectively. The enthalpy difference of the Mg²⁺-equilibrium ΔH_Mg explains the high temperature dependence of the AMD - AM·Mg²⁺D equilibrium and underlines the non-linear behavior of sliding velocity in the Arrhenius plots.