User:Galanyousuf1/sandbox

MerR
MerR is a family of transcriptional activators that are mettaloregulators, they are metal sensing and have evolved to recognize and respond to different metals. They help to regulate intracellular levels of metals that could be essential or toxic to the cell. More specifically the MerR family fall into the category of metal ion responsive cytoplasmic regulators. MerR regulate both its own production and expression

Regulation
The MerR family of transcription activators will respond to the presence of toxic and essential metals. The regulators will directly bind the target metal and initiate transcription via promoters as a result of metal binding. The transcription activators are commonly classified into several groups varying in which metal the transcription factor binds.
 * MerR
 * Recognize Hg2+


 * CueR
 * Recognize Cu+


 * CadR
 * Recognize Cd2+


 * PbrR
 * Recognize Pb2+


 * ZntR
 * Recognize Zn2+

MerR activation of expression of the structural mercuric ion resistance proteins begins at the PmerT operator/promoter site. The apo-MerR dimer binds will bind to the PmerT site (which contains an abnormally long spacer of 19 bp between the -35 and -10 sequences). The target DNA sequence and recruits a σ70 RNA polymerase to the promoter but the transcription is rejected due to the promoter DNA being bent by the apo-MerR homodimer binding. For the metalloregulators to be effective they must be able to recognize the correct promoter and bound by the correct regulator. The correct regulator must respond fast so that there is an appropriate response to the metal ion. The operators/promoters of different MurR regulators will have different dyad symmetrical DNA sequences.

Mechanism Of Action
They use the mechanism DNA distortion. They will recognize a specific DNA sequence promoter and using both apo and holo forms will bind tightly to the DNA promoter. MerR will be bound to the DNA sequence promoter and in the absence of an inducer will repress activity and activate in the presence. MerR is always bound to their respective promoter. A common MerR inducer is Hg2+. In the absence of Hg2+  merR bends the operator-promoter DNA strongly. In the presence of Hg2+  in cell, the Hg2+  will bind to MerR allosterically, resulting in a change in conformation that then allows RNA polymerase to transcribe the gene.

Structure
All MerR metalloregulators are homo dimeric proteins. MerR can be broken down into two domains: the DNA binding domain at the N-terminal and the metal binding domain at the C-terminal. A common feature of the merR regulator proteins is the presence of helix turn helix motif followed by a coiled-coil region.