Unno Masashi, Masuda Shinji, Ono Taka-aki, Yamauchi Seigo
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
J Am Chem Soc. 2006 May 3;128(17):5638-9. doi: 10.1021/ja060633z.
The flavin-adenine-dinucleotide-binding BLUF domain constitutes a new class of blue-light receptors, and the N-terminal domain of AppA is a representative of this family. A crystal structure of the BLUF domain from AppA suggested that a conserved Gln63 forms a hydrogen bond with the flavin N5 atom. Upon light excitation, this residue is proposed to undergo a approximately 180 degrees rotation that leads to a rearrangement of a hydrogen bonding network. However, crystallographic studies on the other BLUF proteins claimed an opposite orientation for the glutamine residue. In this communication, we have revealed the presence of a Gln63-to-N5 hydrogen bond in the dark state of AppA by a combined approach of mutagenesis, spectroscopy, and quantum chemical calculations. The present finding supports the view that the reorientation of the Gln63 side chain is a key event in the signaling state formation of BLUF proteins.
黄素腺嘌呤二核苷酸结合BLUF结构域构成了一类新的蓝光受体，而AppA的N端结构域是该家族的代表。来自AppA的BLUF结构域的晶体结构表明，保守的Gln63与黄素N5原子形成氢键。在光激发时，该残基被认为会发生约180度的旋转，导致氢键网络的重新排列。然而，对其他BLUF蛋白的晶体学研究表明谷氨酰胺残基的方向相反。在本通讯中，我们通过诱变、光谱学和量子化学计算相结合的方法，揭示了AppA在黑暗状态下存在Gln63与N5的氢键。目前的发现支持了这样一种观点，即Gln63侧链的重新定向是BLUF蛋白信号状态形成中的关键事件。
