In recent years, the understanding of cellular bacterial metal homeostasis has advanced considerably, leading to a new paradigm of tightly controlled metal ion distribution. Characterization of metalloregulatory proteins has contributed significantly to this picture, providing important insights into how bacteria handle metals. In vitro transcription run off assays conducted under strict metal buffering conditions, have been used as a powerful tool to calibrate the sensitivity of Zur and CueR, both members of MerR protein family with responses to Zn2+ and Cu1+ respectively. Both proteins sense low free metal concentrations equivalent to less than one atom per cell, corroborating the hypothesis that there is not a pool of free metal ions in the cytosol of bacteria.

The high sensitivity and selectivity of metalloregulatory proteins has been explained in a molecular basis by solving the crystal structure.

CueR structure, solved in collaboration with Prof Alfonso Mondragon's lab, BMBCB Department, Northwestern University

We are interested in applying these and other biophysical techniques to further understand the molecular basis of metal selectivity and sensitivity of other metalloregulatory proteins such as Fur (Fe²⁺ sensor) and MerR (Hg²⁺).

Publications

• Outten, C.E., Outten, F.W. and O'Halloran, T.V. "DNA Distortion Mechanism for Transcriptional Activation by ZntR, a Zn(II)-responsive MerR homologue in E. coli." JBC in press.


• Althaus, E.W., Outten, C.E., Olson, K.E., Cao, H., and O'Halloran, T.V. "The Ferric Uptake Regulation (Fur) Repressor Is a Zinc Metalloprotein" Biochemistry, 1999, 38, 6559-6569.
• Fleissner, G., Reigle, M.D., O'Halloran, T.V. and Spiro, T.G. "UVRR Spectroscopy of the Metal Receptor Site in MerR" J. Amer. Chem. Soc, 1998, 120, 12690-12691.


• Dieckmann, G.R., McRorie, D.K. Tierney, D.L., Utschig, L.M., Singer, C.P. O'Halloran, T.V. Penner-Hahn, J.E., DeGrado, W.F., Pecoraro, V.L. "The De Novo Design of Mercury-Binding Two- and Three-Helical Bundles." J. Amer. Chem. Soc., 1997, 119, 6195-6196.


• Utschig, L., Baynard, T., Strong, C. and O'Halloran, T.V. "Probing the Copper Coordination Chemistry of Rusticyanin and Azurin by 2D 1H-199Hg NMR" Inorg. Chem., 1997, 36, 2926-2927.


• Huffman, D., Utschig, L and O'Halloran, T. V. " Mercury Responsive Gene Regulation and Mercury-199 as a Probe of Protein Structure." in Metal Ions in Biological Systems, H. Sigel, ed., Marcel Dekker, NY, Vol. 34, 1997, 503-526.


• Utschig, L., Wright, J., Dieckmann, G., Pecoraro, V. and O'Halloran, T. "The 199Hg Chemical Shift as a Probe of Coordination Environments in Blue Copper Proteins", Inorg. Chem., 1995, 34, 2497-2498.


• Utschig, L., Bryson, J., O'Halloran, T. "Mercury-199 NMR of the Metal Receptor Site in MerR and Its Protein-DNA Complex", Science, 1995, 268, 380-385.


• Ansari, A.Z., Bradner, J.E., O'Halloran, T.V. "DNA Bend Modulation in a Repressor -to-Activator Switching Mechanism". Nature, 1995, 374, 371-375.