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首页> 外文期刊>Biochemistry >Modulating LOV Domain Photodynamics with a Residue Alteration outside the Chromophore Binding Site
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Modulating LOV Domain Photodynamics with a Residue Alteration outside the Chromophore Binding Site

机译：在发色团结合位点以外的残基改变来调节LOV域光动力学。

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摘要

Phototropins, a class of light-activated protein kinases, are essential for several blue light responses in plants and algae,nincluding phototropism. These proteins contain two internal light, oxygen, and voltage sensitive (LOV) domains, which bind flavinnchromophores and undergo a reversible photochemical formation of a cysteinyl-flavin adduct as part of the light sensing process.nWhile the photodynamic properties of such photosensory domains are dictated by interactions between the chromophore andnsurrounding protein, more distant residues can play a significant role as well. Here we explore the role of the Phe434 residue in thenphotosensory response of the second LOV domain of Avena sativa phototropin 1 (AsLOV2), a model photochemical system fornthese LOV domains. Phe434 is more than 6 Å from the FMN chromophore in AsLOV2; nevertheless, an F434Y point mutation isnlikely to change several structural features of the chromophore binding site, as we demonstrate using molecular dynamicsnsimulations. Transient absorption signals spanning 15 decades in time were compared for wild-type AsLOV2 and the F434Ymutant,nshowing that the latter has significantly altered photodynamics, including (i) a faster intersystemcrossing leading to triplet formationnon a nanosecond time scale, (ii) biphasic formation of adduct-state kinetics on the microsecond time scale, and (iii) greatlynaccelerated ground-state recovery kinetics on a second time scale. We present mechanistic models that link these spectroscopicndifferences to changes in the configuration of the critical cysteine residue and in the chromophore’s accessibility to solvent andnoxygen according toMDtrajectories and purging experiments. Taken together, these results demonstrate the importance of residuesnoutside the chromophore-binding pocket in modulating LOV domain photodynamics.
机译：光化蛋白是一类光激活的蛋白激酶，对于植物和藻类中的几种蓝光反应（包括光致性）至关重要。这些蛋白质包含两个内部的光，氧和电压敏感（LOV）域，这些域与aviavichromophores结合，并在光感测过程中发生半胱氨酰-avin加合物的可逆光化学形成。通过发色团和周围蛋白质之间的相互作用，更远的残基也可以起重要作用。在这里，我们探讨了Phe434残基在Avena sativa肌钙蛋白1（AsLOV2）的第二个LOV域的光敏响应中的作用，该模型是用于这些LOV域的模型光化学系统。 Phe434与AsLOV2中FMN发色团的距离大于6Å；但是，正如我们使用分子动力学模拟所证实的，F434Y点突变很可能会改变发色团结合位点的一些结构特征。比较了野生型AsLOV2和F434Y突变体跨越15年时间的瞬态吸收信号，这表明F434Y突变体的光动力学发生了显着变化，包括（i）更快的系统间穿越导致三重态形成，而不是纳秒级的时间尺度；（ii）双相形成微秒级的加合物状态动力学，以及（iii）第二级的基态恢复动力学大大提高。我们提供了将这些光谱差异与关键半胱氨酸残基的构型变化以及生色团根据MD轨迹和吹扫实验可及性达到溶剂和氧的可利用性变化联系起来的机理模型。综上所述，这些结果证明了在发色团结合口袋之外的残基在调节LOV域光动力学中的重要性。

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