Sandbox Reserved 1053: Difference between revisions

Czr A is a transcriptional repressor protein responsible for the regulation of the 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 while Czr A regulates this process by controlling expression level of Czr B. 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, an inhibitor of Czr A must be readily available to allow full transcription of Czr B when necessary. Czr A is noncompetitively inhibited by the binding of two Zn 2+ ions, which is ideal in that this allows for expression of Czr B, a zinc transporter to be dependent on the relative amount of zinc in the cell.  Czr A displays two different conformations; the first typically binds DNA and has relatively low affinity for Zn 2+, the other binds two Zn 2+ ions and has relatively low affinity for DNA.