Sarkar H K, Song P S
Biochemistry. 1982 Apr 13;21(8):1967-72. doi: 10.1021/bi00537a041.
The phototransformation of the photomorphogenic photoreceptor phytochrome was probed by the intrinsic luminescence of the tryptophan (Trp) residues. The red light absorbing form of phytochrome (Pr) showed a decreased tryptophan phosphorescence intensity, compared to that of the far-red light absorbing form of phytochrome (Pfr), and a delayed fluorescence from the chromophore upon excitation of the tryptophan residues with 290-nm light. The tryptophan phosphorescence in both Pr and Pfr showed decreased lifetimes (0.29 and 1.84 s, respectively) compared to that of the free tryptophan (6.00 s). In addition, the decay kinetics of the delayed fluorescence in Pr showed a short-lifetime component (0.24 s), which is similar to the tryptophan phosphorescence lifetime value. This is due to an efficient triplet-singlet (3Trp-1Pr) energy transfer in the Pr from. The increases in the tryptophan phosphorescence quantum yield and lifetime in the Pfr form have been interpreted on the basis of chromophore reorientation on the protein surface as a result of the Pr lead to Pfr phototransformation. The Stern-Volmer plot of the quenching data further confirms preferential exposure of the tryptophan residues in the Pfr form (46% "exposed' tryptophan residues in the Pr form as compared to 72% in the Pfr form). These results provide strong support for the hydrophobic model of Pfr [Hahn, T. R., & Song, P. S. (1981) Biochemistry 20, 2602-2609).
通过色氨酸（Trp）残基的固有发光来探究光形态建成光受体光敏色素的光转化。与远红光吸收型光敏色素（Pfr）相比，红光吸收型光敏色素（Pr）的色氨酸磷光强度降低，并且在用290nm光激发色氨酸残基时，发色团发出的延迟荧光也有所延迟。与游离色氨酸（6.00s）相比，Pr和Pfr中的色氨酸磷光寿命均缩短（分别为0.29和1.84s）。此外，Pr中延迟荧光的衰减动力学显示出一个短寿命成分（0.24s），这与色氨酸磷光寿命值相似。这是由于Pr中存在高效的三重态-单重态（3Trp-1Pr）能量转移。基于Pr向Pfr光转化导致蛋白质表面发色团重新定向，对Pfr形式中色氨酸磷光量子产率和寿命的增加进行了解释。猝灭数据的Stern-Volmer图进一步证实了Pfr形式中色氨酸残基的优先暴露（Pr形式中有46%的色氨酸残基“暴露”，而Pfr形式中为72%）。这些结果为Pfr的疏水模型提供了有力支持[哈恩，T.R.，&宋，P.S.（1981）《生物化学》20，2602-2609]。
