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spinqualitylabelsall models 3D Representation of CzrA with Zn Bound Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Contents 1 CzrA 2 Biological Function 3 Structural Overview 4 DNA Bound State 5 Zinc Ligand(s) 6 References

CzrA

Biological Function

Structural Overview

DNA Bound State

The have been found to occur at the Ser 54 and 57 along with His 58. These residues are likely to interact with the 5'-TGAA sequence found in the half-site of the DNA. These residues are found in the N terminal of the R helix. The residues involved in the are Val 42 and Gln 53. This was experimentally determined by replacing the Gln and Val with Ala residues and measuring the binding capacity; In a previously published article^[1], the DNA bound state of CzrA was tested by using the known critical residues for DNA interactions. Critical residues, Gln53, Val42, Ser54, Ser57, and His58, were replaced with Ala and then compared to the kinetics of the wild type protein. Replacing only the Q53 and V42 residues resulted in an 11-fold and 160-fold decrease in K_a, respectively. Other residues such as S54, S57, and H58 were also replaced with Ala residues, and it was found that these mutations caused binding similar to the fully inhibited Zn²⁺ bound state. Table 1 in this article show the different K_observed, and the measured decrease in K_observed for each mutation. The bind between the DNA and the protein can be attributed to losing certain intermolecular forces such as possible hydrogen bonding when changing from Gln and Ala, and a loss of London Dispersion forces in the Val to Ala change.

The differences in binding favorability can also be seen when comparing the ΔG for the Apo-state vs. the DNA bound state and the Zinc vs. the Zinc and DNA bound state. These ΔGs were found to be -15.2kcal/mol and -9kcal/mol respectively^[1]. This agrees with previously published data showing the Zinc binding inhibits the affinity the protein has to DNA.

Zinc Ligand(s)

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References

Arunkumar A., Campanello G., Giedroc D. (2009). Solution Structure of a paradigm ArsR family zinc sensor in the DNA-bound state. PNAS 106:43 18177-18182

Chakravorty D., Giedroc D., Merz K., Lee C., Wang B. (2012). Simulations of Allosteric Motions in the Zinc Sensor CzrA. JCAS 134 3367-3376