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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Structural Water Cluster As a Possible Proton Acceptor in the Adduct Decay Reaction of Oat Phototropin 1 LOV2 Domain
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Structural Water Cluster As a Possible Proton Acceptor in the Adduct Decay Reaction of Oat Phototropin 1 LOV2 Domain

机译：结构水团簇可能是质子受体在燕麦光蛋白1 LOV2结构域加合物衰变反应中的作用

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摘要

LOV domains (Light, Oxygen, Voltage) are the light-sensory modules of phototropins, the blue-light photoreceptor kinases in plants, and of a wide variety of flavoproteins found in all three domains of life. These 12 kDa modules bind a flavin chromophore (FMN or FAD) noncovalently and undergo a photochemical activation in which the sulfur atom of a conserved cysteine forms an adduct to the C(4a) carbon of the flavin. The adduct breaks spontaneously in a base-catalyzed reaction involving a rate-limiting proton-transfer step, regenerating the dark state in seconds. This photocycle involves chromophore and protein structural changes that activate the C-terminal serine/threonine kinase. Previous studies {Biochemistry 2007, 46, 7016-7021) showed that decreased hydration obtained at high glycerol concentrations stabilizes the adduct state in a manner similar to that attained at low temperatures, resulting in much longer adduct decay times. This kinetic effect was attributed to an increased protein rigidity that hindered structural fluctuations necessary for the decay reaction. In this work, we studied the adduct decay kinetics of oat phototropin 1 (phot1) LOV2 at varying hydration using a specially designed chamber that allowed for measurement of UV-visible and FTIR spectra of the same samples. Therefore, we obtained LOV protein concentrations, adduct decay kinetics, and the different populations of bound water by deconvolution of the broad water absorption peak around 3500 cm~(-1) A linear dependence of the adduct decay rate constant on the concentration of double and triple hydrogen-bonded waters strongly suggests that the adduct decay is a pseudo-first-order reaction in which both the adduct and the strongly bound waters are reactants. We suggest that a cluster of strongly bound water functions as the proton acceptor in the rate-limiting step of adduct decay.
机译：LOV域（光，氧，电压）是光养蛋白，植物中的蓝光感光受体激酶以及在生活的所有三个域中发现的多种黄素蛋白的光传感模块。这些12 kDa的模块非共价结合黄素发色团（FMN或FAD），并进行光化学活化，其中保守的半胱氨酸的硫原子与黄素的C（4a）碳形成加合物。加合物在涉及限速质子转移步骤的碱催化反应中自发断裂，在数秒内再生出黑暗状态。该光循环涉及激活C端丝氨酸/苏氨酸激酶的生色团和蛋白质结构变化。先前的研究（Biochemistry 2007，46，7016-7021）表明，在高甘油浓度下降低的水合作用以类似于在低温下获得的方式稳定了加合物状态，从而导致更长的加合物衰变时间。该动力学效应归因于增加的蛋白质刚性，该蛋白质刚性阻碍了衰变反应所必需的结构波动。在这项工作中，我们使用专门设计的腔室研究了燕麦水合蛋白1（phot1）LOV2在不同水合作用下的加合物衰减动力学，该腔室可测量相同样品的UV-可见光谱和FTIR光谱。因此，我们通过在3500 cm〜（-1）附近的宽吸水峰解卷积来获得LOV蛋白浓度，加合物衰变动力学和不同的结合水种群。加合物衰变速率常数对double和三重氢键结合水强烈表明加合物的衰变是伪一级反应，其中加合物和牢固结合的水都是反应物。我们建议在加合物衰变的限速步骤中，一束强烈结合的水起质子受体的作用。

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