Fundación Instituto Leloir, IIBBA-CONICET, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
J Mol Biol. 2012 Jun 29;420(1-2):112-27. doi: 10.1016/j.jmb.2012.04.006. Epub 2012 Apr 11.
Light-oxygen-voltage (LOV) domains are blue-light-activated signaling modules present in a wide range of sensory proteins. Among them, the histidine kinases are the largest group in prokaryotes (LOV-HK). Light modulates the virulence of the pathogenic bacteria Brucella abortus through LOV-HK. One of the striking characteristic of Brucella LOV-HK is the fact that the protein remains activated upon light sensing, without recovering the basal state in the darkness. In contrast, the light state of the isolated LOV domain slowly returns to the dark state. To gain insight into the light activation mechanism, we have characterized by X-ray crystallography and solution NMR spectroscopy the structure of the LOV domain of LOV-HK in the dark state and explored its light-induced conformational changes. The LOV domain adopts the α/β PAS (PER-ARNT-SIM) domain fold and binds the FMN cofactor within a conserved pocket. The domain dimerizes through the hydrophobic β-scaffold in an antiparallel way. Our results point to the β-scaffold as a key element in the light activation, validating a conserved structural basis for light-to-signal propagation in LOV proteins.
光氧电压（LOV）结构域是存在于多种感觉蛋白中的蓝光激活信号模块。其中，组氨酸激酶是原核生物中最大的一类（LOV-HK）。光通过 LOV-HK 调节致病性细菌布鲁氏菌的毒力。布鲁氏菌 LOV-HK 的一个显著特点是，蛋白质在光感应后仍然保持激活状态，而在黑暗中不会恢复到基础状态。相比之下，分离的 LOV 结构域的光状态会缓慢恢复到黑暗状态。为了深入了解光激活机制，我们通过 X 射线晶体学和溶液 NMR 光谱学对 LOV-HK 的 LOV 结构域在黑暗状态下的结构进行了表征，并探索了其光诱导的构象变化。LOV 结构域采用 α/β PAS（PER-ARNT-SIM）结构域折叠，并在保守口袋内结合 FMN 辅因子。结构域通过疏水的β-支架以反平行方式二聚化。我们的结果表明β-支架是光激活的关键因素，验证了 LOV 蛋白中光信号传递的保守结构基础。
