Chemistry of photoproteins as interface between bioactive molecules and protein function
Bioluminescence of Okinawan squid includes a photoprotein named "Symplectin" which gives light by addition of Na+ (or K+). The chromophore is covalently bound-imidazopyrazinone analog to protein. Symplectin was extracted with 0.6M KC1 and was analyzed to be composed of 3 different molecular-size proteins. Symplectin A, the smallest photoproteins, was purified by gel permeation chromatography to have 15kd by MALDVTOF mass spectrometry. The molecular mechanism of this luminescence is described. Bioluminescence is also applied for trace analyses and the chromophore in some new fireflies is chemically analyzed. We made a very sensitive detection system of luciferin to a detection limit of 10-'6 moY1Opl by using immobilized luciferase and a single photon-counter. An example of the firefly luminescence application is demonstrated in an inhibitory-assay of protein phosphatase activity by inhibitors in the same class of tautomycidokadaic acid.