Heidi Hu/Sandbox 1
From Proteopedia
|
Heavy metals such as iron, nickel, copper, and zinc are important cofactors for the functions of many different metalloenzymes. High levels of these heavy metals can also damage cellular components, therefore intracellular levels of metals are tightly regulated within the cell. One of the ways that bacteria can regulate intracellular metal levels is by increasing the amount of metal efflux proteins. CsoR and RcnR are members of a large family of metal-responsive DNA-binding proteins, both of which regulate the transcription of metal-specific efflux proteins. Transcriptional regulation activity of CsoR is only responsive to the binding of Cu(I); whereas RcnR is only responsive to the binding of Ni(II) or Co(II).
In Escherichia coli apo-RcnR blocks the transcription of nickel and cobalt efflux protein RcnA by binding to its promoter region. Upon Ni(II) or Co(II)-binding, RcnR is released from the DNA allowing the transcription of RcnA and therefore the efflux of Ni(II) and Co(II). CsoR has been characterized in Bacillus subtilis and Mycobacterium tuberculosis to release from the promoter regions of copper-efflux operons upon binding of Cu(I). The analogous functions of CsoR and RcnR in addition to local sequence similarity (25% identical, 56% similar) between the two proteins suggests a conserved mode of function in this family of metal-responsive DNA-binding proteins.
