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首页> 外文期刊>Journal of Molecular Biology >CRYSTAL STRUCTURE OF CELLULAR RETINOIC ACID BINDING PROTEIN I SHOWS INCREASED ACCESS TO THE BINDING CAVITY DUE TO FORMATION OF AN INTERMOLECULAR BETA-SHEET
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CRYSTAL STRUCTURE OF CELLULAR RETINOIC ACID BINDING PROTEIN I SHOWS INCREASED ACCESS TO THE BINDING CAVITY DUE TO FORMATION OF AN INTERMOLECULAR BETA-SHEET

机译：由于形成分子间β-片，我发现细胞维甲酸结合蛋白的晶体结构增加了结合腔的进入

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摘要

A recombinant form of murine ape-cellular retinoic acid binding protein I (apo-CRABPI) has been purified and crystallized at pH 5.0, and the crystal structure has been refined to an R-factor of 19.6% at a resolution of 2.7 Angstrom. CRABPI binds all-trans retinoic acid and some retinoic acid metabolites with nanomolar affinities. Coordinates of the hole form of CRABP were not available during the early stages of the study, and in spite of numerous homologs of known structure, phases were not obtainable through molecular replacement. Instead, an interpretable electron density map was obtained by multiple isomorphous replacement methods after improvement of the heavy-atom parameters with density modified trial phases. Two molecules of apo-CRABPI occupy the P3(1)21 asymmetric unit and are related by pseudo 2-fold rotational symmetry Unique conformational differences are apparent between the two molecules. In all of the family members studied to date, there is a lack of hydrogen bonds between two of the component beta-strands resulting in a gap in the interstand hydrogen bonding pattern. In the crystallographic dimer described here, a continuous intermolecular beta-sheet is formed by using this gap region. This is possible because of an 8 Angstrom outward maximum displacement of the tight turn between the third and fourth beta-strands on one of the molecules. The result is a double beta-barrel containing two apo-CRABPI molecules with a more open, ligand-accessible binding cavity, which has not been observed in other structures of a family of proteins that bind hydrophobic ligands. (C) 1995 Academic Press Limited [References: 69]
机译：重组的鼠类猿细胞视黄酸结合蛋白I（apo-CRABPI）的重组形式已在pH 5.0下纯化和结晶，并且晶体结构已精制到19.6％的R因子，分辨率为2.7埃。 CRABPI以纳摩尔亲和力结合全反式维甲酸和一些维甲酸代谢物。在研究的早期阶段，没有CRABP孔形式的坐标，尽管有许多已知结构的同系物，但不能通过分子置换获得相。取而代之的是，在使用密度修改的试验阶段改进重原子参数之后，通过多种同构置换方法获得了可解释的电子密度图。 apo-CRABPI的两个分子占据P3（1）21不对称单元，并通过伪2倍旋转对称性关联。这两个分子之间存在独特的构象差异。迄今为止，在所有研究的家族成员中，两个组分β链之间都缺乏氢键，导致支架之间的氢键模式出现了缺口。在这里描述的晶体学二聚体中，通过使用该间隙区域形成连续的分子间β-片。这是可能的，因为一个分子上的第三和第四β链之间的紧密匝的向外最大位移为8埃。结果是含有两个带有更开放的，配体可及的结合腔的apo-CRABPI分子的双β桶，这在结合疏水性配体的蛋白质家族的其他结构中尚未观察到。 （C）1995 Academic Press Limited [参考：69]

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