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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >pH-Dependent Picosecond Structural Dynamics in the Distal Pocket of Nitrophorin 4 Investigated by 2D IR Spectroscopy
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pH-Dependent Picosecond Structural Dynamics in the Distal Pocket of Nitrophorin 4 Investigated by 2D IR Spectroscopy

机译：二维红外光谱法研究硝化蛋白4远端腔中pH依赖的皮秒结构动力学

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摘要

Nitrophorin 4 (NP4) belongs to a family of pH-scnsitive, nitric oxide (NO) transporter proteins that undergo a large structural change from a closed to an open conformation at high pH to allow for NO delivery. Measuring the pH-dependent structural dynamics in NP4—NO around the ligand binding site is crucial for developing a mechanistic understanding of NO binding and release. In this study, we use coherent two-dimensional infrared (2D IR) spectroscopy to measure picosecond structural dynamics sampled by the nitrosyl stretch in NP4—NO as a function of pH at room temperature. Our results show that both the closed and open conformers of the protein are present at low (pD 5.1) and high (pD 7.9) pH conditions. The closed and open conformers are characterized by two frequencies of the nitrosyl stretching vibration labeled A0 and A1, respectively. Analysis of the 2D IR line shapes reveals that at pD 5.1, the closed conformer experiences structural fluctuations arising from solvation dynamics on a ~3 ps time scale. At pD 7.9, both the open and closed conformers exhibit fluctuations on a ~1 ps time scale. At both pD conditions, the closed conformers maintain a static distribution of structures within the experimental time window of 100 ps. This is in contrast to the open conformer, which is able to interconvert among its substates on a ~100 ps time scale. Our results directly measure the time scales of solvation dynamics in the distal pocket, the flexibility of the open conformation at high pH, and the rigidity of the closed conformers at both pH conditions. We discuss how the pH-dependent equilibrium structural fluctuations of the nitrosyl ligand measured in this study are related to the uptake and delivery of nitric oxide in NP4.
机译：硝化蛋白4（NP4）属于pH敏感的一氧化氮（NO）转运蛋白家族，该蛋白在高pH下会经历从封闭构象到开放构象的较大结构变化，以允许NO传递。测量配体结合位点周围NP4-NO中pH依赖性的结构动力学对于建立对NO结合和释放的机械理解至关重要。在这项研究中，我们使用相干二维红外（2D IR）光谱技术来测量NP4-NO中亚硝酰基拉伸所得到的皮秒结构动力学，其与室温下pH的关系。我们的结果表明，蛋白质的封闭和开放构象异构体均在低（pD 5.1）和高（pD 7.9）pH条件下存在。闭合和开放构象异构体的特征在于分别标记为A0和A1的亚硝酰基拉伸振动的两个频率。对2D IR线形的分析表明，在pD 5.1时，封闭的构象体会在约3 ps的时间尺度上经历由溶剂化动力学引起的结构波动。在pD 7.9时，打开和关闭的构象异构体都在〜1 ps的时间范围内表现出波动。在两种pD条件下，封闭的构象异构体均在100 ps的实验时间窗口内保持结构的静态分布。这与开放式配置器相反，后者能够在〜100 ps的时间尺度上在其子状态之间进行相互转换。我们的结果直接测量了远端囊袋中溶剂化动力学的时间尺度，在高pH下开放构象的柔韧性以及在两个pH条件下封闭构象异构体的刚度。我们讨论在这项研究中测量的亚硝酰基配体的pH依赖性平衡结构性波动如何与NP4中一氧化氮的吸收和传递有关。

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