The PA-GFP entry in FlyBase represents a photoactivatable green fluorescent protein which is derived from the naturally occurring fluorescent protein encoded by the Aequorea victoria GFP gene (UniProtKB:P42212) and which is photoactivatable due to the presence of a T203H mutation in the chromophore (PMID:12228718). Upon activation with UV light (390-415 nm), PA-GFP is converted from a weakly fluorescent protein to a bright green fluorescent state with an excitation peak of 504nm and an emission peak of 517nm in vitro, resulting in a 100-fold increase in green fluorescence (PMID:12228718, PMID:20664080, PMID:18057027). The A206K mutation that disrupts dimerization (PMID:11988576) may also be present, resulting in a monomeric form if this is case.