Part:BBa_K143036

Xylose operon regulatory protein

Transcription is regulated by proteins which bind operator sequences around the transcription start site. These proteins can positively affect transcription (activators) or negatively affect transcription (reppresors). Some repressor proteins can be inactivted however by addition of an inducer, such as xylose.

XylR if the regulator protein for the Xylose operon in B. subtilis#1 and is responsible for ensuring that in the absence of xylose the xylose metabolism proteins are not expressed. Though endogenous to B. subtilis, to minimise the leakage of a xylose inducible promoter XylR should be over-expressed. In the presence of xylose, the XylR tetramer is unable to bind DNA and so transcription resumes.

It must be noted that in all B. subtilis strains that do not have the Xylose operon knocked out the xylose inducer will gradually be metabolised by the host

XylR was used in conjunction with the Xylose operon promoter (BBa_K143014