title: Multi-probe relaxation dispersion measurements increase sensitivity to protein dynamics.
abstract: Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion measurements are a valuable tool for the characterization of structural transitions on the micro-millisecond timescale. While the measurement of (15)N relaxation dispersion is now routine, the measurements with alternative nuclei remain limited. Here we report (15)N as well as (1)H R2 relaxation dispersion measurements of the N23PP/S148A "dynamic knockout" mutant of dihydrofolate reductase. The (1)H dispersion measurements are complementary to (15)N data as many additional residues are observed to have dispersive behavior for the (1)H nucleus. Simultaneous fitting of the dispersion profiles for the two nuclei increases the accuracy of exchange parameters determined for individual residues and clustered groups of residues. The different sensitivity of the two nuclei to changes in backbone torsional angles, ring currents, and hydrogen bonding effects provides important insights into the nature of the structural changes that take place during the exchange process. We observe clear evidence of direct and indirect hydrogen bond effects for the (15)N and (1)H chemical shift changes in the active-site, modulation of ring current shielding in the CD-loop and backbone torsional changes in a cluster of residues associated with the C-terminus. This work demonstrates the power of combined (1)H and (15)N probes for the study of backbone dynamics on the micro-millisecond timescale though the analysis of chemical shift changes.
authors.affiliation: Department of Integrative Structural and Computational Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA. wright@scripps.edu.
authors.forename: R Bryn
authors.initials: RB
authors.lastname: Fenwick
authors.affiliation: Department of Integrative Structural and Computational Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA. wright@scripps.edu.
authors.forename: David
authors.initials: D
authors.lastname: Oyen
authors.affiliation: Department of Integrative Structural and Computational Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA. wright@scripps.edu.
authors.forename: Peter E
authors.initials: PE
authors.lastname: Wright
mesh_terms: D020134:Catalytic Domain; D004926:Escherichia coli / Q000201:enzymology; D006860:Hydrogen Bonding; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism
chemical_list: D014364:Tryptophan; D013762:Tetrahydrofolate Dehydrogenase