Sandbox Reserved 1051: Difference between revisions

Zinc is an allosteric inhibitor to CzrA. Two zinc⁺² ions may bind to the dimer, at the location of the <scene name='69/694218/Alpha_5_helices/2'> alpha 5 </scene> helix from each monomer. As zinc binds, the alpha 5 helices <scene name='69/694218/2kjc_zinc_bound/1'>swing down</scene> to inhibit the DNA binding residues. Furthermore, CzrA must be in its dimer form for zinc to bind. The <scene name='69/694218/Spacefill_with_zinc_pockets/1'>zinc binding pocket</scene> is formed by two residues from each monomer, so zinc⁺² cannot bind to the monomer. The <scene name='69/694218/Zinc_residues/1'>zinc binding site</scene> is formed by Asp84 and His86 from one monomer, and His97 and His100 from the other monomer.  

The zinc⁺² ion forms a tetrahedral complex with the four residues (Figure 1). This allows other metal ions to act as allosteric inhibitors to CzrA. Any metal that may form a tetrahedral complex will have some affinity for CzrA, assuming it is not too large to fit into the pocket. However, the metal binding pocket of CzrA has been optimized  to bind zinc⁺² with the highest affinity. As CzrA is a transcriptional repressor, binding of zinc⁺² to the dimer will activate the czr operon. Zinc ⁺² is preferred as CzrB opens a zinc⁺² channel, allowing the excess zinc ions to export the cell.  

== References ==

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