The iATPSnFR(1.0) entry in FlyBase represents a genetically encoded single-wavelength fluorescent sensor for ATP, as described in PMID:30755613. It is based on the epsilon subunit of Bacillus sp. PS3 F[[0]]F[[1]]-ATP synthase (UniProtKB:P07678), into which a circularly permuted form of sfGFP has been inserted, flanked by linkers. Upon binding to ATP, conformational changes in the F[[0]]F[[1]]-ATP synthase epsilon subunit result in an increase in fluorescence. Purified iATPSnFR(1.0) has a maximum dF/F of ~2.4 and an EC[[50]] of ~120 μM.