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首页> 外文期刊>IUCrJ >Homochiral and racemic MicroED structures of a peptide repeat from the ice-nucleation protein InaZ
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Homochiral and racemic MicroED structures of a peptide repeat from the ice-nucleation protein InaZ

机译：冰核蛋白InaZ的肽的手性和外消旋MicroED结构重复

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摘要

The ice-nucleation protein InaZ from Pseudomonas syringae contains a large number of degenerate repeats that span more than a quarter of its sequence and include the segment GSTSTA. Ab initio structures of this repeat segment, resolved to 1.1 Å by microfocus X-ray crystallography and to 0.9 Å by the cryo-EM method MicroED, were determined from both racemic and homochiral crystals. The benefits of racemic protein crystals for structure determination by MicroED were evaluated and it was confirmed that the phase restriction introduced by crystal centrosymmetry increases the number of successful trials during the ab initio phasing of the electron diffraction data. Both homochiral and racemic GSTSTA form amyloid-like protofibrils with labile, corrugated antiparallel β-sheets that mate face to back. The racemic GSTSTA protofibril represents a new class of amyloid assembly in which all-left-handed sheets mate with their all-right-handed counterparts. This determination of racemic amyloid assemblies by MicroED reveals complex amyloid architectures and illustrates the racemic advantage in macromolecular crystallography, now with submicrometre-sized crystals.
机译：丁香假单胞菌的冰核蛋白InaZ包含大量简并重复序列，这些重复序列覆盖了其序列的四分之一以上，并包括GSTSTA片段。从外消旋和同手性晶体中确定了该重复片段的从头算结构，该结构从微焦点X射线晶体学解析为1.1Å，而通过冷冻EM方法MicroED解析为0.9Å。评估了外消旋蛋白晶体对MicroED结构测定的好处，并证实了通过晶体中心对称引入的相位限制在电子衍射数据的从头定相期间增加了成功试验的次数。同手性和外消旋的GSTSTA都形成淀粉样的原纤维，具有不稳定的，波纹状的反平行β片层，彼此面对面地配对。外消旋的GSTSTA原纤维代表了一类新的淀粉样蛋白装配体，其中全左手床单与其全右手床相对。通过MicroED对消旋淀粉样蛋白组装体的测定揭示了复杂的淀粉样蛋白体系结构，并说明了大分子晶体学中的消旋体优势（现在具有亚微米级晶体）。

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