Part:BBa_K1590003

Chromate responsive promoter

The promoter pChr is suspected to be inducible by chromate.

Usage and Biology

This promoter is found upstream of the ChrBACF - operon in Ochrobactrum tritici 5bvl1, located in the transposable element TnOtChr of 7189bp length.

Ochrobactrum tritici 5bvl1 was discovered in 2004 in a chromate contaminated wastewater treatment facility. A specific characteristic of this strain was that it could both, reduce Cr(VI) and be resistant to it at the same time. Previously characterised strains were either resistant or could reduce chromate. Over the last 10 years the group that discovered it started working out the underlying mechanisms of this set of characteristics.

The ChrBACF - operon, expressed from the Pchr - promoter led to the expression of the downstream genes chrA, chrB, chrC, and chrF. chrA was found to express and efflux pump, whereas the gene product of chrB was identified as being a chromate-inducible regulator of Pchr. Additionally, chrC and chrF were found to confer tolerance to superoxides.

Pchr itself is believed to be regulated by the chromate-sensitive repressor <i>chrB. This has made it a candidate for a biological sensor of chromate contamination in e.g. rivers (Branco et al.), or in milk (iGEM BIT 2013).