Bocola Marco, Schwaneberg Ulrich, Jaeger Karl-Erich, Krauss Ulrich
Lehrstuhl für Biotechnologie, RWTH Aachen University Aachen, Germany.
Forschungszentrum Jülich, Institut für Molekulare Enzymtechnologie, Heinrich Heine University Düsseldorf Jülich, Germany ; Forschungszentrum Jülich, Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie Jülich, Germany.
Front Mol Biosci. 2015 Oct 1;2:55. doi: 10.3389/fmolb.2015.00055. eCollection 2015.
The modularity of light, oxygen, voltage (LOV) blue-light photoreceptors has recently been exploited for the design of LOV-based optogenetic tools, which allow the light-dependent control of biological functions. For the understanding of LOV sensory function and hence the optimal design of LOV-based optogentic tools it is essential to gain an in depth atomic-level understanding of the underlying photoactivation and intramolecular signal-relay mechanisms. To address this question we performed molecular dynamics simulations on both the dark- and light-adapted state of PpSB1-LOV, a short dimeric bacterial LOV-photoreceptor protein, recently crystallized under constant illumination. While LOV dimers remained globally stable during the light-state simulation with regard to the Jα coiled-coil, distinct conformational changes for a glutamine in the vicinity of the FMN chromophore are observed. In contrast, multiple Jα-helix conformations are sampled in the dark-state. These changes coincide with a displacement of the Iβ and Hβ strands relative to the light-state structure and result in a correlated rotation of both LOV core domains in the dimer. These global changes are most likely initiated by the reorientation of the conserved glutamine Q116, whose side chain flips between the Aβ (dark state) and Hβ strand (light state), while maintaining two potential hydrogen bonds to FMN-N5 and FMN-O4, respectively. This local Q116-FMN reorientation impacts on an inter-subunit salt-bridge (K117-E96), which is stabilized in the light state, hence accounting for the observed decreased mobility. Based on these findings we propose an alternative mechanism for dimeric LOV photoactivation and intramolecular signal-relay, assigning a distinct structural role for the conserved "flipping" glutamine. The proposed mechanism is discussed in light of universal applicability and its implications for the understanding of LOV-based optogenetic tools.
光、氧、电压（LOV）蓝光光感受器的模块化特性最近已被用于基于LOV的光遗传学工具的设计，这些工具能够实现对生物功能的光依赖性控制。为了理解LOV的传感功能，进而对基于LOV的光遗传学工具进行优化设计，深入了解其潜在的光激活和分子内信号传递机制的原子水平细节至关重要。为了解决这个问题，我们对PpSB1-LOV（一种短二聚体细菌LOV光感受器蛋白，最近在持续光照下结晶）的暗适应和光适应状态进行了分子动力学模拟。在光状态模拟过程中，就Jα卷曲螺旋而言，LOV二聚体整体保持稳定，但在FMN发色团附近观察到一个谷氨酰胺的明显构象变化。相比之下，在暗状态下采样到多个Jα螺旋构象。这些变化与Iβ和Hβ链相对于光状态结构的位移一致，并导致二聚体中两个LOV核心结构域的相关旋转。这些整体变化很可能是由保守谷氨酰胺Q116的重新定向引发的，其侧链在Aβ（暗状态）和Hβ链（光状态）之间翻转，同时分别与FMN-N5和FMN-O4保持两个潜在的氢键。这种局部的Q116-FMN重新定向影响了一个亚基间盐桥（K117-E96），该盐桥在光状态下稳定，因此解释了观察到的迁移率降低。基于这些发现，我们提出了一种二聚体LOV光激活和分子内信号传递的替代机制，为保守的“翻转”谷氨酰胺赋予了独特的结构作用。根据普遍适用性及其对理解基于LOV的光遗传学工具的意义，对所提出的机制进行了讨论。
