Masaryk University, Faculty of Science, National Centre for Biomolecular Research, Kotlářská 2, 61137 Brno, Czech Republic
Backbone dynamics of mouse major urinary protein I (MUP-I) was studied by NMR relaxation. Data were collected for a complex of MUP-I with its natural
pheromonal ligand, 2-sec-4,5-dihydrothiazole, and for the free protein. The measured relaxation rates were analyzed using the spectral density mapping.
Graphical analysis of the spectral density values pro- vided an unbiased qualitative picture of the internal motions. Varying temperature greatly improved reliability of the analysis.
Quantitative parameters describing the dynamics on picosecond to nanosecond time scale were obtained using simultaneous data fitting at multiple
temperatures. Both qualitative and quantitative analyses showed that the backbone flexibility on the fast time scale is slightly increased upon
pheromone binding, in accordance with the previously reported results. Zero-frequency spectral density values revealed conformational changes on the
microsecond to millisecond time scale. Measurements at different temperatures allowed to monitor temperature depencence of the motional parameters.
Molecular dynamics simulations were performed for the free and pheromone-bound proteins using explicite solvent. Correlation functions and frequency-dependent order parameters were calculated from protein coordinates. The calculated motional parameters were compared to the results of the relaxation
measurements. Combination of experimental and simulated data provided a datailed picture of the molecular motions.
This work was supported by Grant No. 203/00/0511 from Grant Agency of the Czech Republic.