In the Q-mate CymR system, repression of gene expression is mediated by the cumate repressor protein CymR bound to operator sites in the absence of the inducer molecule cumate. With cumate present, CymR binds to cumate and undergoes a conformational change resulting in its release from the operator sites which permits transgene expression. The reporter construct consists of three components: a strong promoter, the CymR binding sites (cumate operator sequences, CuO), and a reporter or a transgene.
The Q-mate CymR system makes use of the cym operon, which in Pseudomonas putida F1 controls the expression of genes intervening in the transformation of p-cymene (found in volatile oils from several plant species) to p-cumate T.
The cmt operon, located downstream of the cym operon, controls the further degradation of the cumate molecule. Upstream of the cym operon lies a regulatory gene, cymR, encoding a 28-kDa repressor molecule (CymR), which monitors expression of both the cym and cmt operons and is induced by p-cumate. CymR is in a DNA-binding configuration only in the absence of cymene and cumate.
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