Figure 5
A proposed model for Ca2+ binding to NOX5's EF1 and EF2. A microscopic binding model is proposed based on the studies of -1EF+2EF and +1EF-2EF that determine their microscopic binding constants (kI and kII for EF1 and EF2) and the studies of NCaBD that determine their overall binding constants, β1 and β2. Due to the equilibrium among all states, the equation β2 = KI × KII,I = KII × KI,II was used to determine intrinsic binding constants of EF1 in the presence of Ca2+-bound EF2 (KI,II) and of EF2 in the presence of Ca2+-bound EF1 (KI,II). The microscopic cooperativity constant, c12, was determined by the equation: c12 = KII,I/KII = KI,II/KI.