Saccharomyces cerevisiae will be modified in such a way that the yeast cell should
function as a biosensor for the human chorionic gonadotropin hormone (hCG). This hormone is
produced in the body during pregnancy and consequently, the idea is for the biosensor to function
as a simple pregnancy test. To construct the biosensor, the human luteinizing hormone receptor (LH/CG), which is the receptor that hCG binds to with high affinity, will be expressed and coupled with with the already existing pheromone pathway in yeast. Consequently, binding of hCG should result in activation of the pathway. Two genes encoding tryptophanase and a monooxygenase respectively will also be introduced into the yeast strain. These enzymes catalyze the conversion of tryptophan to indigo and will be coupled with pheromone-induced promoters. Hence, detection of hCG should result in the production of bio-indigo. In order to ensure hCG to pass the yeast cell wall, the gene encoding a cell wall protein will also be deleted.
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