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首页> 外文期刊>Biochemistry >CHARACTERIZATION OF CONFORMATIONAL PREFERENCES IN A PARTLY FOLDED PROTEIN BY HETERONUCLEAR NMR SPECTROSCOPY - ASSIGNMENT AND SECONDARY STRUCTURE ANALYSIS OF HEN EGG-WHITE LYSOZYME IN TRIFLUOROETHANOL [Review]
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CHARACTERIZATION OF CONFORMATIONAL PREFERENCES IN A PARTLY FOLDED PROTEIN BY HETERONUCLEAR NMR SPECTROSCOPY - ASSIGNMENT AND SECONDARY STRUCTURE ANALYSIS OF HEN EGG-WHITE LYSOZYME IN TRIFLUOROETHANOL [Review]

机译：核磁共振波谱法表征部分折叠蛋白质的构型优势-三氟乙醇中鸡白蛋白溶菌酶的赋值和二级结构分析[综述]

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2D and 3D heteronuclear NMR methods have been used to characterize the structure of hen egg-white lysozyme in a partially folded state using uniformly N-15-labeled protein. This state is formed by the denaturation of the protein in 70% trifluoroethanol (TFE)/30% water (v/v) and is characterized by substantial helical secondary structure in the absence of extensive tertiary interactions. N-15-filtered 3D NOESY and TOCSY experiments have allowed the sequential assignment of resonances for all but 2 of the 126 main chain amide nitrogen atoms and of the majority of main and side chain proton resonances. The conformation of the polypeptide chain was characterized by analysis of the pattern of NOEs, H-alpha> chemical shift perturbations,H- ?3J(H?N,H-H?(alpha)-coupling constants, and hydrogen exchange protection. These NMR parameters are highly complementary and are consistent with a model for the TFE state in which six regions of the polypeptide chain are substantially ordered in helical conformations, The structure in different regions however, shows different levels of persistency. Five of the helices exhibit significant protection of amide hydrogens against exchange with solvent and are located in regions of the polypeptide which are helical in the native state. By contrast, helical structures of greater flexibility are observed both as extensions to the native-like helices and as a nonnative structure in the region of the molecule which forms the C-terminal part of the beta-sheet in the native state. No specific structural preferences are detected in regions corresponding to the long loop and to the N-terminal part of the P-sheet of native lysozyme. A combination of local features of the polypeptide chain, including the predicted propensities of residues for helix formation and for their participation in N- and C-terminal helix capping interactions, allows the conformational behavior of the polypeptide chain of hen lysozyme to be rationalized for this partially folded state. The analysis implies that the nonnative structures are a result of interactions which are local to the polypeptide chain. These, and the highly persistent native-like structures, give insight into species which form early during folding.
机译：已使用2D和3D异核NMR方法使用均匀的N-15标记蛋白表征部分折叠状态的鸡蛋清溶菌酶的结构。这种状态是由蛋白质在70％三氟乙醇（TFE）/ 30％水（v / v）中的变性形成的，其特征是在没有广泛三级相互作用的情况下具有基本的螺旋二级结构。经过N-15过滤的3D NOESY和TOCSY实验允许对126个主链酰胺氮原子中的2个以及除大部分主链和侧链质子共振以外的所有共振进行顺序分配。通过分析NOE的模式，H-α>化学位移扰动，H-？3J（H？N，HH？α-耦合常数和氢交换保护）来表征多肽链的构象。具有高度互补性，并且与TFE状态模型一致，在该模型中，多肽链的六个区域基本上呈螺旋状排列，但是不同区域的结构表现出不同的持久性，其中五个螺旋显示出对酰胺的显着保护作用氢反对与溶剂交换，并且位于天然状态下呈螺旋状的多肽区域中，相比之下，观察到具有更大柔韧性的螺旋结构既作为对天然样螺旋的延伸，又作为非天然结构存在于该区域。在天然状态下形成β-折叠的C端部分的分子，在与lon对应的区域中未检测到特定的结构偏好g环和天然溶菌酶P-sheet的N-末端部分。多肽链局部特征的组合，包括预计的残基形成螺旋以及参与N和C末端螺旋加帽相互作用的残基倾向，可使母鸡溶菌酶多肽链的构象行为合理化。部分折叠状态。分析暗示非天然结构是多肽链局部相互作用的结果。这些以及高度持久的类似原生的结构，可以洞悉折叠初期形成的物种。

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