FIGURE 4.

The derived local overall tumbling time for CaM in the CaM:SEF2-1mp complex (○) (a, left). The error in the individual values of the CaM:SEF2-1mp complex is ±0.9 ns (derived from the error in R₁ and R₂). The average of the α-helices are indicated with red lines and their standard deviations as black lines. The right panel shows a schematic figure of the CaM:SEF2-1mp complex that is compatible with both the classical NMR data from Larsson et al. (22) and the global structure information derived from the relaxation data presented here. The axial ratio of the diffusion tensor (2Dz/(Dx + Dy)) is approximated to be ∼1.8, assuming a cylinder-shaped molecule. In panel b (left) the back calculated from the CaM:SMLCK complex (9) are shown. Via hydrodynamic calculations the diffusion tensor was determined to be cylinder symmetric with τ_l = 7.4 ns at 308 K. The dimensions of the complex and the orientation of the diffusion tensor are shown in panel b (right). Panel c shows the back calculated from the CaM:SMLCK complex assuming that the molecule has rotated by 90° with respect to the original diffusion tensor giving (τ//y). In panel d the (τ//y) values from the C-terminal residues in panel c (scaled to the size and shape of the CaM:SEF2-1mp complex) are plotted against the of the corresponding residues in the CaM:SEF2-1mp complex. A clear correlation is seen between these values, indicating that the main axis of the diffusion tensor has indeed rotated ∼90° in the CaM:SEF2-1mp complex compared with that of the CaM:SMLCK complex.