Fast events in protein folding: Relaxation dynamics of secondary and tertiary structure in native apomyoglobin
Fast events in protein folding: Relaxation dynamics of secondary and tertiary structure in native apomyoglobin
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DOI：
10.1073/pnas.94.8.3709
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发表时间：
1997-04-15
影响因子：
11.1
通讯作者：
Dyer, RB
中科院分区：
文献类型：
--
作者：
Gilmanshin, R;Williams, S;Dyer, RB
我们报告的快速弛豫动力学的“本地”apomyoglobin（pH 5.3）后10 ns，激光诱导的温度跳变。使用时间分辨红外光谱的结构动力学探测。在多肽骨架的酰胺I吸收内监测的红外动力学表现出两个不同的弛豫阶段，其具有不同的光谱特征并且发生在非常不同的时间尺度上（nu = 1633 cm（-1）48 ns; nu = 1650 cm-1，tau = 132 μ s）。我们将这两个光谱分量分配给蛋白质中的离散子结构：溶剂化的螺旋结构（1633 cm（-1））和通过螺旋间三级相互作用保护免受溶剂化的天然螺旋（1650 cm（-1））。从60 ℃下观察到的弛豫推断的折叠速率系数分别为k（f（溶剂化））=（7至20）x 10（6）s（-1）和k（f（天然））= 3.6 x 10（3）s（-1）。较快的速率被解释为溶剂化螺旋形成的固有速率，而较慢的速率被解释为确定天然螺旋的三级接触的形成速率。因此，在60摄氏度下，螺旋形成先于三级结构形成超过三个数量级。此外，不同的热力学和动力学观察到的脱辅基肌红蛋白的亚结构表明，他们折叠独立，或准独立。观察到的非均匀折叠的脱辅基肌红蛋白是显着的，考虑到相对较小的尺寸和结构简单的这种蛋白质。
We report the fast relaxation dynamics of ''native'' apomyoglobin (pH 5.3) following a 10-ns, laser-induced temperature jump. The structural dynamics are probed using time-resolved infrared spectroscopy. The infrared kinetics monitored within the amide I absorbance of the polypeptide backbone exhibit two distinct relaxation phases which have different spectral signatures and occur on very different time scales (nu = 1633 cm(-1) 48 ns; nu = 1650 cm-1, tau = 132 mu s). We assign these two spectral components to discrete substructures in the protein: helical structure that is solvated (1633 cm(-1)) and native helix that is protected from solvation by interhelix tertiary interactions (1650 cm(-1)). Folding rate coefficients inferred from the observed relaxations at 60 degrees C are k(f(solvated)) = (7 to 20) x 10(6) s(-1) and k(f(native)) = 3.6 x 10(3) s(-1), respectively. The faster rate is interpreted as the intrinsic rate of solvated helix formation, whereas the slower rate is interpreted as the rate of formation of tertiary contacts that determine a native helix. Thus, at 60 degrees C helix formation precedes the formation of tertiary structure by over three orders of magnitude in this protein. Furthermore, the distinct thermodynamics and kinetics observed for the apomyoglobin substructures suggest that they fold independently, or quasi-independently. The observation of inhomogeneous folding for apomyoglobin is remarkable, given the relatively small size and structural simplicity of this protein.