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.