The invention provided herein relates to sequence determinants that elicit certain levels of gene expression and methods for obtaining engineered ligand-responsive gene switches comprising these sequence determinants. More particularly, the invention provided herein relates to molecular building blocks (i.e., discrete nucleotide sequences), synthetic ligand-responsive gene switches comprising an assembly of these molecular building blocks, and methods of using synthetic ligand-responsive gene switches as customizable and controllable expression systems and sensors.
STATEMENT REGARDING FEDERALLY FUNDED RESEARCH
 This invention was made with government support under GM045844 awarded by the National Institutes of Health and DE-FC02-07ER64494 and DE-FG02-04ER25627 awarded by the US Department of Energy. The government has certain rights in the invention.