Regensburg 2010 – scientific programme

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SYMR: Symposium Nuclear Magnetic Resonance: from Applications in Condensed-Matter Physics to New Frontiers

SYMR 7: Biopolymers and Biomaterials

SYMR 7.11: Topical Talk

Wednesday, March 24, 2010, 17:00–17:30, H37

Recognition dynamics and kinetics for ubiquitin — •Christian Griesinger — MPI for Biophysical Chemistry, Goettingen, Germany

We measured residual dipolar couplings in a large number of alignment media for ubiquitin and derived an ensemble with the EROS method that reflects motion up to the microsecond time scale. The ensemble fits very well the NMR parameters used for the refinement and cross validates other unused NMR parameters such as J-couplings and other dipolar couplings. The ensemble has an rmsd of approximately 1Åand shows large fluctuations in loops as well as in secondary structure elements. The ensemble reflects mainly motion on the previously inaccessible time scale between ns and microseconds. Its implications for molecular recognition will be discussed. We have further measured the time scale of the recognition dynamics and find a previously unobservable sub-β-peak in dielectric relaxation spectroscopy in solution that can be explained by a modulation of the ion conductance by the conformational ensemble. From the temperature dependence of this effect, on can expect to slow down the dynamics in supercooled solution to approximately 50 µs. Indeed, relaxation dispersion measurements in supercooled solution reveal that the time scale of major conformational interconversions is 50 to 100 µs and that the above mentioned ensembles predict correctly the relaxation dispersion data. Furthermore, correlated motion in the ensemble has been quantified experimentally with cross correlated relaxation. We find that the above mentioned rdc derived ensembles agree much better with the cross correlated relaxation data than ensembles that reflect only individual motion.