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Biological Function

Czr A is a transcriptional repressor protein responsible for the regulation of the Chromosome Determined Zinc Responsible (Czr) operon. The Czr operon contains genes for the proteins Czr A and Czr B. Czr B is a Zinc transport protein which moves Zn 2+ out of a cell. Czr A regulates this process by controlling the degree to which Czr B is expressed. When relatively low amounts of zinc are present in the cell Czr A will bind to DNA,preventing the progression of RNA polymerase and thus inhibiting expression of Czr B. Decreased expression of Czr B results in the ability of the cell to retain Zn 2+ more readily. Because Czr A and Czr B are transcribed as part of the same operon, there must be a way that Czr A is inhibited to allow full transcription of Czr B. Czr A is inhibited by the binding of two Zn 2+ ions, which is ideal considering that this mechanism allows for Zn 2+ concentration inside the cell to determine the need for Zn 2+ transport out of the cell. Zn 2+ competitively inhibits the binding of DNA to Czr A. Czr A has two distinct conformations, one of which binds Zn 2+ with very high affinity that has virtually no affinity towards DNA binding, the other having a high affinity for DNA binding but very little affinity for Zn 2+.

DNA Binding

Zinc Binding

Zinc Ligand(s)

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References

1. ↑ Hanson, R. M., Prilusky, J., Renjian, Z., Nakane, T. and Sussman, J. L. (2013), JSmol and the Next-Generation Web-Based Representation of 3D Molecular Structure as Applied to Proteopedia. Isr. J. Chem., 53:207-216. doi:http://dx.doi.org/10.1002/ijch.201300024
2. ↑ Herraez A. Biomolecules in the computer: Jmol to the rescue. Biochem Mol Biol Educ. 2006 Jul;34(4):255-61. doi: 10.1002/bmb.2006.494034042644. PMID:21638687 doi:10.1002/bmb.2006.494034042644