Backbone Dynamics of Tet Repressor 8
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- 作者：Benedetta Vergani ; Martin Kintrup ; Wolfgang Hillen ; Hans Lami ; Etienne Pié ; mont ; Elisa Bombarda ; Patrizia Alberti ; Silvia M. Doglia ; and Marie Chabbert
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：March 14, 2000
- 年：2000
- 卷：39
- 期：10
- 页码：2759 - 2768
- 全文大小：132K
- 年卷期：v.39,no.10(March 14, 2000)
- ISSN：1520-4995
文摘
A set of single Trp mutants of class B Tet repressor (TetR), in which Trp residues are locatedfrom positions 159 to 167, has been engineered to investigate the dynamics of the loop joining the 
-helices8 and 9. The fluorescence anisotropy decay of most mutants can be described by the sum of threeexponential components. The longest rotational correlation time, 30 ns at 10 
C, corresponds to the overallrotation of the protein. The shortest two components, on the subnanosecond and nanosecond time scale,are related to internal motions of the protein. The initial anisotropy, in the 0.16-0.22 range, indicates theexistence of an additional ultrafast motion on the picosecond time scale. Examination of physical modelsfor underlying motions indicates that librational motions of the Trp side chain within the rotameric 
1 ×2 potential wells contribute to the picosecond depolarization process, whereas the subnanosecond andnanosecond depolarization processes are related to backbone dynamics. In the absence of inducer, theorder parameters of these motions, about 0.90 and 0.80 for most positions, indicate limited flexibility ofthe loop backbone. Anhydrotetracycline binding to TetR induces an increased mobility of the loop on thenanosecond time scale. This suggests that entropic factors might play a role in the mechanism of allosterictransition.
-helices8 and 9. The fluorescence anisotropy decay of most mutants can be described by the sum of threeexponential components. The longest rotational correlation time, 30 ns at 10 C, corresponds to the overallrotation of the protein. The shortest two components, on the subnanosecond and nanosecond time scale,are related to internal motions of the protein. The initial anisotropy, in the 0.16-0.22 range, indicates theexistence of an additional ultrafast motion on the picosecond time scale. Examination of physical modelsfor underlying motions indicates that librational motions of the Trp side chain within the rotameric 1 ×2 potential wells contribute to the picosecond depolarization process, whereas the subnanosecond andnanosecond depolarization processes are related to backbone dynamics. In the absence of inducer, theorder parameters of these motions, about 0.90 and 0.80 for most positions, indicate limited flexibility ofthe loop backbone. Anhydrotetracycline binding to TetR induces an increased mobility of the loop on thenanosecond time scale. This suggests that entropic factors might play a role in the mechanism of allosterictransition.