Crystal structure of the transcriptional repressor PagR of Bacillus anthracis

1 Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA 2 Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, 4301 W Markham St, Little Rock, AR 72205-7199, USA PagR is a transcriptional repressor in Bacillus anthracis that controls the chromosomal S-layer genes eag and sap , and downregulates the protective antigen pagA gene by direct binding to their promoter regions. The PagR protein sequence is similar to those of members of the ArsR repressor family involved in the repression of arsenate-resistance genes in numerous bacteria. The crystal structure of PagR was solved using multi-wavelength anomalous diffraction (MAD) techniques and was refined with 1.8 Å resolution diffraction data. The PagR molecules form dimers, as observed in all SmtB/ArsR repressor family proteins. In the crystal lattice four PagR dimers pack together to form an inactive octamer. Model-building studies suggest that the dimer binds to a DNA duplex with a bend of around 4 °. Correspondence Kottayil I. Varughese KIVarughese{at}uams.edu Abbreviations: MAD, multi-wavelength anomalous diffraction Present address: Department of Molecular Biosciences, 8041 Haworth Hall, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA. The atomic coordinates and structure factors for PagR (PDB ID 2ZKZ ) have been deposited in the Protein Data Bank, Research Collaboratory for Structural bioinformatics, Rutgers University, New Brunswick, NJ ( http://www.rcsb.org ). A supplementary sequence alignment is available with the online version of this paper.