Hahn T R, Song P S
Biochemistry. 1981 Apr 28;20(9):2602-9. doi: 10.1021/bi00512a036.
8-Anilinonaphthalene-1-sulfonate (ANS) complexes with phytochrome, exhibiting a higher affinity for the Pfr form of phytochrome than for the Pr form. ANS fluorescence is enhanced by the additional binding of ANS to Pfr upon transformation of phytochrome from Pr to Pfr. The specific site of ANS binding appears to be the hydrophobic surface area of the protein, which becomes at least partially exposed in the Pfr form. An exposed, hydrophobic surface area in the Pfr phytochrome has been confirmed by the effects of ANS on the phototransformation of phytochrome. ANS accelerates the Pr leads to Pfr phototransformation, and it inhibits Pfr leads to Pr photoreversion and dark reversion. These effects are interpretable in terms of competitive binding of ANS to the chromophore binding site. Binding of ANS results in a drastic bleaching of the chromophore's absorption bands at 660 and 730 nm, particularly of the latter. This can be attributed to the exposed chromophore, which tends to resume a cyclic conformation with concomitant blue shift and hypochromism of the Qy bands. Sodium dithionite counteracts the inhibitory effects of ANS on the dark reversion of Pfr to Pr, and its effect on the biphasic kinetics of the reversion has been discussed in terms of the Pfr model proposed.
8-苯胺基萘-1-磺酸盐（ANS）与光敏色素结合，对光敏色素的Pfr形式表现出比对Pr形式更高的亲和力。当光敏色素从Pr转化为Pfr时，ANS与Pfr的额外结合会增强ANS荧光。ANS结合的特定位点似乎是蛋白质的疏水表面积，其在Pfr形式中至少部分暴露。ANS对光敏色素光转化的影响证实了Pfr光敏色素中存在暴露的疏水表面积。ANS加速Pr向Pfr的光转化，并抑制Pfr向Pr的光逆转和暗逆转。这些效应可以用ANS与发色团结合位点的竞争性结合来解释。ANS的结合导致发色团在660和730nm处的吸收带急剧漂白，尤其是后者。这可以归因于暴露的发色团，其倾向于恢复环状构象，伴随着Qy带的蓝移和减色效应。连二亚硫酸钠抵消了ANS对Pfr向Pr暗逆转的抑制作用，并且根据所提出的Pfr模型讨论了其对逆转双相动力学的影响。
