EFFECTIVENESS OF THE ACCESSORY YELLOW FLUORESCENT PROTEIN IN THE BACTERIAL LUCIFERASE REACTION CORRELATES WITH THE LIFETIME OF THE PEROXYHEMIACETAL INTERMEDIATE - THE STEREOCHEMISTRY OF THE REACTION

In the in vitro reaction of Vibrio fischeri Y-1 luciferase, the depend ence of the initial luminescence intensity (I-O) and its rate of decaj t (k(d)) on the chain-length of the aliphatic aldehyde are greatly alt ered by the presence of yellow fluorescent protein (YFP), which functi ons as an accessory emitter. Whereas with no YFP both k(d) and I-O are maximum for chain lengths greater than or equal to 12, the fraction o f the light emitted from the accessory chromophore, measured as the ra tio of yellow to blue light (Y/B), is greater with shorter chain-lengt h aldehydes, Thus, aldehydes that are least efficient in the absence o f YFP are more efficient for causing yellow emission in its presence, These results are interpreted on the basis of the expected lifetimes o f the peroxyhemiacetals with which YFP interacts: high values of k(d) reflect short peroxyhemiacetal lifetimes, hence lass chance of interac tion with YFP, The critical dependence on aldehyde chain-length underl ines the importance of stereochemical factors in the bacterial reactio n, which are discussed here in the framework of a chemically initiated electron exchange luminescence model.