Sandbox Reserved 1051

This Sandbox is Reserved from 02/09/2015, through 05/31/2016 for use in the course "CH462: Biochemistry 2" taught by Geoffrey C. Hoops at the Butler University. This reservation includes Sandbox Reserved 1051 through Sandbox Reserved 1080.

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CzrACzrA

<StructureSection load='2KJB' size='340' side='right' caption='The dimer CzrA' scene=> This is a default text for your page '. Click above on edit this page' to modify. Be careful with the < and > signs. You may include any references to papers as in: the use of JSmol in Proteopedia or to the article describing Jmol to the rescue.

Structural OverviewStructural Overview

CzrA functions as a dimer. The dimerize at the czr operon, repressing gene transcription. Each monomeric unit contains seen in purple and displayed in yellow. While the function of the beta sheets are not yet known, key helices regulate the binding of DNA and Zn ⁺² . The is the location of DNA binding and the contains the Zn ⁺² binding site. As Zn ⁺² binds, the alpha 4 helices are repressing their DNA binding ability.

Binding of DNABinding of DNA

The have been found to be the SER 54 and 57 along with HIS 58.

Zinc BindingZinc Binding

Zinc is an allosteric inhibitor to CzrA. Two Zn ⁺² ions may bind to the dimer, at the location of the helix from each monomer. As zinc binds, the alpha 5 helices to inhibit the DNA binding residues. Furthermore, CzrA must be in its dimer form for zinc to bind. The is formed by two residues from each monomer, so Zn⁺² cannot bind to the monomer. The 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 Zn⁺² with the highest affinity. As CzrA is a transcriptional repressor, binding of Zn⁺² to the dimer will activate the czr operon. Zn⁺² is preferred as CzrB opens a Zn⁺² channel, allowing the excess zinc ions to export the cell.

Figure 1:Zn⁺² tetrahedral binding complex