How binding of different metals affects the structure of nickel regulator protein NikR

INOR 148

Christine M. Phillips, cmp_chem@mit.edu1, Eric R. Schreiter, eric_sch@mit.edu2, Yayi Guo1, and Catherine L. Drennan, cdrennan@mit.edu1. (1) Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., 56-546, Cambridge, MA 02139, (2) NIH Protein Research Center, University of Puerto Rico Mayaguez, Mayaguez, PR 00681
E. coli NikR regulates the uptake of nickel by suppressing the transcription of the nik operon, which encodes for the nickel uptake transporter, NikABCDE. In vitro studies of NikR have shown that it is capable of binding a range of divalent metal ions in addition to Ni2+, leaving the mechanism of nickel-selective suppression in question. We have determined the structures of the metal binding domain (MBD) of NikR in the apo form and in complex with Ni2+, Cu2+, and Zn2+. We observe that Cu2+ binds in a similar manner to Ni2+, but with longer bonds and distorted geometry. Crystals grown in the presence of Zn2+ reveal a protein structure similar to apo MBD with a disordered α3 helix. We have drawn connections between these structural findings and previously reported binding constants for full-length NikR to DNA. These findings support the hypothesis that ordering of the α3 helix is crucial for repressor activation.
 

Bioinorganic Chemistry: DNA and RNA
1:30 PM-5:30 PM, Sunday, August 19, 2007 BCEC -- 211, Oral

Division of Inorganic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007