Difference between revisions of "Part:BBa K1420004"

Revision as of 01:49, 10 October 2014

merR family transcriptional regulator, regulatory protein for mer operon

merR, located upstream of the rest of the mer operon mercury resistance genes, serves to regulate the mer operon by activating transcription in the presence of Hg(II) and acting as a weak repressor in the absence of Hg(II). The MerR protein contains a C-terminal effector-binding region that recognizes ionic mercury. Upon binding Hg(II) a MerR homodimer forms. The protein’s N-terminal helix-turn-helix DNA binding domain can now bind the palindromic merR binding sequence located between the -35 and -10 elements of the PmerT inducible promoter. Figure 1 gives a detailed outline of the intergenic sequence involved in this conformational change.

This promoter has an unusually long spacer sequence of 19 bp that only allows for weak ribosome binding. Typically MerR will also bind this region in the absence of Hg(II) to inhibit an translation of the mer operon genes. The MerR/Hg(II) dimer structurally alters the promoter upon binding, allowing for tight ribosome binding and transcription of the downstream genes.

The effector binding region of merR family proteins can vary allowing for great diversity in merR-like promoters that can respond to a variety of heavy metals as well as antibiotics and oxidative stress. This variable nature of merR family proteins makes them a valuable tool for various heavy metal detection and bioremediation.

Sequence and Features