Photoreaction Mechanism of Blue Light Photoreceptor Tll0078 from Thermosynechococcus elongatus BP-1

Abstract

Purified Tll0078 protein of Thermosynechococcus elongatus BP-1 expressed in E.coli binds one FAD molecule. The absorption spectrum of the FAD moiety shows peaks at 467 nm, 438 nm and 383 nm. Under the illumination of the blue light, the peaks are red shifted to 479 nm, 448 nm and 389 nm, respectively. The shift decays with a t_1/2 of 6.7 seconds at room temperature. We measured the absorption changes, the lifetime of fluorescence of FAD and the transient absorption change induced by pulse laser excitation. The quantum efficiency of the reaction was calculated to be about 30 %. Based on the results, we will discuss changes in the molecular structure of FAD and protein.