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This structure is determined mainly by residual dipolar couplings
measured in A liquid crystalline Pf1 medium. The structure calculation
scheme, described in the paper, is based on the idea of refining existing
structural models against dipolar couplings to derive the correct
structure. Here a total of 305 backbone dipolar couplings are used to refine the backbone structure. Additionally, 35 sidechain dipolar couplings and 81 3-bond J couplings are used to determine the sidechain
chi1 and chi2 rotamers as well as the presence of rotameric averaging. A
total of three structures (model 1-3) were calculated starting from the 1. A crystal structure of Ca-calmodulin (PDB entry 1EXR), the NMR structure
of apo-calmodulin (1F70), and the crystal structure of Ca-ligated parvalbumin (1CDP). The convergence of refinement is
indicated by the small average RMSD between the three calculated
structures and the average coordinates (0.26 A for backbone and 0.90 for
all heavy atoms). During the three-stage simulated annealing described in
the paper, restraints are included for most previously established
hydrogen bonds, but have only minute effects (< 0.3 A) on the final structure.
X-PLOR
NMR Ensemble Information
Conformer Selection Criteria
structure with the lowest dipolar energy
Conformers Calculated Total Number
3
Conformers Submitted Total Number
3
Representative Model
2 (lowest dipolar energy)
Additional NMR Experimental Information
Details
A total of five sets of dipolar couplings are measured, including the one-bond NH, CAHA, C'CA, and NC' couplings, and the two-bond C'HA couplings.
Additionally, the CBHB dipolar couplings were measure to assign chi-1 rotamers for locked sidechains.