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Structure and Dynamics of the Transcriptional Regulator MerR

by Hao-Bo Guo

MerR homodimer binds to the operator DNA of some bacteria that carry the mercury-resistant, or mer, gene, which encodes the mer proteins that can detoxify the mercury contaminant. Expression of the mer gene is regulated by MerR at transcriptional level, i.e., the transcription by RNA polymerase (RNAP) is repressed by MerR in the absence of the mercury cation Hg(II), but is activated when Hg(II) is bound to MerR.

Combining small-angle X-ray scattering (SAXS) and molecular dynamics (MD) simulations, we have studied the structure and dynamics of MerR upon Hg(II)-binding. The MD structure was constructed by homology modeling from the crystal structure of CueR, a MerR-family protein that is responsible to Cu(I). The MD simulations were in good agreement with the SAXS data and, revealed a large-amplitude (~20 Angs.), slow (~10 ns) opening-and-closing vibration in Hg(II)-MerR. MD simulation of CueR also indicated that this vibration may exist in other MerR-family members. Moreover, this study suggests a transcription activation mechanism of MerR, i.e., the inducer-binding at the metal-binding domain (MBD) may allosterically trigger a conformational dynamics at the DNA-binding domain (DBD) that is ~30 Angs. away from the MBD, and may result in underwinding of the DNA operator to activate the transcription initiation by RNAP.

The movies show the global dynamics and the opening-and-closing dynamics of Hg(II)-MerR.


       Hg-MerR_MD          Hg-MerR_PCA2
                  MOVIE 1                                  MOVIE 2




Guo, H.-B.; Johs, A.; Parks, J. M.; Olliff, L.; Miller, S. M.; Summers, A. O.; Liang, L. and Smith, J. C.
Structure and Conformational Dynnamics of the Metalloregulator MerR upon Binding of Hg(II).
J. Mol. Biol. 2010, 398, 555-568.

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