Figure 6.

Second Mg²⁺ decreases ADP motion. (A) rms fluctuations of ADP phosphates and MgII in ADP·2Mg and ADP·1Mg-type MD simulations. Phosphorus atoms and MgII were aligned in each trajectory; fluctuations about the mean conformation describe motion of just phosphate·MgII atoms. ADP·2Mg simulations show less phosphate flexibility than ADP·1Mg-type simulations. (B) Comparison of two representative simulations: ADP·2Mg (black) and ADP·1Mg + Protonated D145 (gray). Ellipsoids represent 50% probability position of atom position relative to the CDK2 domain mean position. Phosphate oxygens in ADP·1Mg-type simulations are more mobile than phosphate oxygens in ADP·2Mg simulations.