Two-dimensional 1H nuclear magnetic resonance studies of the half-saturated (Ca2+)1 state of calbindin D9k : Further implications for the molecular basis of cooperative Ca2+ binding
Calbindin D9k exhibits cooperative binding of two calcium ions, hence study of the half-saturated states of the protein is critical to understanding the binding process. However, the half-saturated states are not significantly populated under equilibrium conditions. To circumvent this problem, an absolutely conserved glutamic acid residue in the C-terminal binding site (site II) has been mutated t