Solution structure of a paradigm ArsR family zinc sensor in the DNA-bound state.
Staphylococcus aureus CzrA is a zinc-dependent transcriptional repressor from the ubiquitous ArsR family of metal sensor proteins. Zn(II) binds to a pair of intersubunit C-terminal alpha5-sensing sites, some 15 A distant from the DNA-binding interface, and allosterically inhibits DNA binding. This regulation is characterized by a large allosteric coupling free energy (DeltaGc) of approximately +6 kcal mol(-1), the molecular origin of which is poorly understood. Here, we report the solution quaternary structure of homodimeric CzrA bound to a palindromic 28-bp czr operator, a structure that provides an opportunity to compare the two allosteric "end" states of an ArsR family sensor. Zn(II) binding drives a quaternary structural switch from a "closed" DNA-binding state to a low affinity "open" conformation as a result of a dramatic change in the relative orientations of the winged helical DNA binding domains within the dimer. Zn(II) binding also effectively quenches both rapid and intermediate timescale internal motions of apo-CzrA while stabilizing the native state ensemble. In contrast, DNA binding significantly enhances protein motions in the allosteric sites and reduces the stability of the alpha5 helices as measured by H-D solvent exchange. This study reveals how changes in the global structure and dynamics drive a long-range allosteric response in a large subfamily of bacterial metal sensor proteins, and provides insights on how other structural classes of ArsR sensor proteins may be regulated by metal binding.
Arunkumar
Alphonse I
AI
Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA.
Campanello
Gregory C
GC
Giedroc
David P
DP
D000494:Allosteric Regulation; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D013211:Staphylococcus aureus / Q000737:chemistry* / Q000378:metabolism; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
D001426:Bacterial Proteins; C120278:CzrA protein, Staphylococcus aureus; D004268:DNA-Binding Proteins; D004247:DNA; D015032:Zinc