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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >ONE SEQUENCE, TWO FOLDS - A METASTABLE STRUCTURE OF CD2
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ONE SEQUENCE, TWO FOLDS - A METASTABLE STRUCTURE OF CD2

机译：一个序列，两个折叠-CD2的亚稳态结构

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摘要

When expressed as part of a glutathione S-transferase fusion protein the NH2-terminal domain of the Lymphocyte cell adhesion molecule CD2 is shown to adopt two different folds. The immunoglobulin superfamily structure of the major (85%) monomeric component has previously been determined by both x-ray crystallography and NMR spectroscopy, We now describe the structure of a second, dimeric, form present in about 15% of recombinant CD2 molecules. After denaturation and refolding in the absence of the fusion partner, dimeric CD2 is converted to monomer, illustrating that the dimeric form represents a metastable folded state. The crystal structure of this dimeric form, refined to 2.0-Angstrom resolution, reveals two domains with overall similarity to the IgSF fold found in the monomer. However, in the dimer each domain is formed by the intercalation of two polypeptide chains. Hence each domain represents a distinct folding unit that can assemble in two different ways. In the dimer the two domains fold around a hydrophilic interface believed to mimic the cell adhesion interaction at the cell surface, and the formation of dimer can be regulated by mutating single residues at this interface. This unusual misfolded form of the protein, which appears to result from inter- rather than intramolecular interactions being favored by an intermediate structure formed during the folding process, illustrates that evolution of protein oligomers is possible from the sequence for a single protein domain. [References: 31]
机译：当表达为谷胱甘肽S-转移酶融合蛋白的一部分时，淋巴细胞粘附分子CD2的NH2末端结构域显示出两个不同的折叠。主要（85％）单体成分的免疫球蛋白超家族结构先前已通过X射线晶体学和NMR光谱确定。我们现在描述第二个二聚体形式的结构，该结构存在于约15％的重组CD2分子中。在不存在融合伴侣的情况下变性并重新折叠后，二聚体CD2转化为单体，说明该二聚体形式代表亚稳折叠状态。精制至2.0埃分辨率的这种二聚体形式的晶体结构揭示了两个与单体中发现的IgSF折叠总体相似的结构域。然而，在二聚体中，每个结构域是由两条多肽链的插入形成的。因此，每个域代表一个可以以两种不同方式组装的独特折叠单元。在二聚体中，两个结构域围绕亲水界面折叠，而亲水界面被认为模拟了细胞表面的细胞粘附相互作用，并且二聚体的形成可以通过使该界面处的单个残基突变来调节。这种蛋白质的异常折叠形式，似乎是由于折叠过程中形成的中间结构促进了分子间相互作用，而不是分子间相互作用所致，这说明蛋白质寡聚体可能从单个蛋白质结构域的序列进化而来。 [参考：31]

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