Fast Structure-Based Assignment of ~(15)N HSQC Spectra of Selectively ~(15)N-Labeled Paramagnetic Proteins

摘要

A novel strategy for fast NMR resonance assignment of ~(15)N HSQC spectra of proteins is presented. It requires the structure coordinates of the protein, a paramagnetic center, and one or more residue-selectively ~(15)N-labeled samples. Comparison of sensitive undecoupled ~(15)N HSQC spectra recorded of paramagnetic and diamagnetic samples yields data for every cross-peak on pseudocontact shift, paramagnetic relaxation enhancement, cross-correlation between Curie-spin and dipole-dipole relaxation, and residual dipolar coupling. Comparison of these four different paramagnetic quantities with predictions from the three-dimensional structure simultaneously yields the resonance assignment and the anisotropy of the susceptibility tensor of the paramagnetic center. The method is demonstrated with the 30 kDa complex between the N-terminal domain of the ε subunit and the θ subunit of Escherichia coli DNA polymerase III. The program PLATYPUS was developed to perform the assignment, provide a measure of reliability of the assignment, and determine the susceptibility tensor anisotropy.