Sandbox Reserved 1051: Difference between revisions
No edit summary |
No edit summary |
||
| Line 12: | Line 12: | ||
The <scene name='69/694219/Serandhisresidues/1'>main DNA binding residues</scene> have been found to be the SER 54 and 57 along with HIS 58. | The <scene name='69/694219/Serandhisresidues/1'>main DNA binding residues</scene> have been found to be the SER 54 and 57 along with HIS 58. | ||
== Zinc Binding == | == Zinc Binding == | ||
Zinc is an allosteric inhibitor to CzrA. Two zinc<sup> +2 </sup> 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. As CzrA is a transcriptional repressor, binding of zinc to the dimer will activate the czr operon. 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 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. | Zinc is an allosteric inhibitor to CzrA. Two zinc<sup> +2 </sup> 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. As CzrA is a transcriptional repressor, binding of zinc<sup>+2</sup> to the dimer will activate the czr operon. 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<sup>+2</sup> 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 ion forms a tetrahedral complex with the four residues (Figure 1). This allows other metal ions to act as allosteric inhibitors to CzrA. | The zinc<sup>+2</sup> 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 is of a size to optimize zinc<sup>+2</sup> affinity. Zinc <sup>+2</sup> is preferred as CzrB opens a zinc<sup>+2</sup> channel, allowing the excess zinc ions to export the cell. | ||
== References == | == References == | ||
<references/> | <references/> | ||