The present invention provides an alternative strategy for optimizing the signal to noise ratio of a given receptor. Specifically, the present inventi on provides receptor mutants having an increased signal to noise ratio. In one preferred embodiment, the present invention provides receptor mutants having a decreased level of basal activity. As part of this aspect, the present invention provides a mutant serotonin receptor and a mutant CCR-3 receptor, each having decreased basal activity. In another preferred embodiment, the present invention provides receptor mutants having an increased maximal leve l of ligand induced signaling. Such receptors optimize the signal to noise rat io of a receptor and provide, for example, for more sensitive screens for drug discovery.
MUTATION INDUCED OPTIMIZATION OF RECEPTOR SIGNAL TO NOISE RATIO