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首页> 外文期刊>Acta crystallographica. Section D, Structural biology. >Grappling with anisotropic data, pseudo-merohedral twinning and pseudo-translational noncrystallographic symmetry: a case study involving pyruvate kinase
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Grappling with anisotropic data, pseudo-merohedral twinning and pseudo-translational noncrystallographic symmetry: a case study involving pyruvate kinase

机译：面对各向异性数据,pseudo-merohedral孪生和pseudo-translationalnoncrystallographic对称:一个案例研究包括丙酮酸激酶

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Pyruvate kinase is a key regulatory enzyme involved in the glycolytic pathway. The crystal structure of Escherichia coli type I pyruvate kinase was first solved in 1995 at 2.5 angstrom resolution. However, the space group was ambiguous, being either primitive orthorhombic (P2(1)2(1)2(1)) or C-centred orthorhombic (C222(1)). Here, the structure determination and refinement of E. coli type I pyruvate kinase to 2.28 angstrom resolution are presented. Using the same crystallization conditions as reported previously, the enzyme was found to crystallize in space group P2(1). Determination of the space group was complicated owing to anisotropic data, pseudo-translational noncrystallographic symmetry and the pseudo-merohedrally twinned nature of the crystal, which was found to have very close to 50% twinning, leading to apparent orthorhombic symmetry and absences that were not inconsistent with P2(1)2(1)2(1). The unit cell contained two tetramers in the asymmetric unit (3720 residues) and, when compared with the orthorhombic structure, virtually all of the residues could be easily modelled into the density. Averaging of reflections into the lower symmetry space group with twinning provided tidier electron density that allowed similar to 30 missing residues of the lid domain to be modelled for the first time. Moreover, residues in a flexible loop could be modelled and sulfate molecules are found in the allosteric binding domain, identifying the pocket that binds the allosteric activator fructose 1,6-bisphosphate in this isozyme for the first time. Lastly, we note the pedagogical benefits of difficult structures to emerging crystallographers.
机译：丙酮酸激酶是一个关键的调节酶参与糖酵解途径。大肠杆菌I型丙酮酸的结构激酶在1995年首次解决了2.5埃决议。模棱两可的,原始的斜方晶系的(P2(1) 2(1) 2(1))或C-centred斜方晶系的(C222(1))。精致的大肠杆菌I型丙酮酸激酶2.28埃分辨率。结晶条件一样报道在此之前,酶被发现结晶在空间群P2(1)。由于各向异性数据组复杂,pseudo-translational noncrystallographic对称和pseudo-merohedrally孪生的性质水晶,发现非常接近50%双晶,导致明显的斜方晶系的对称和缺席,没有不一致与P2(1) 2(1) 2(1)。四聚体的不对称单元(3720残留)相比,斜方晶系的结构,几乎所有的残留物容易模仿成密度。反思下对称空间群与孪生整理者电子密度使类似于30失踪的残留物盖子域为第一次。此外,残留在一个灵活的循环模仿和硫酸分子中发现的变构绑定域,确定口袋里结合变构激活果糖1, 6-bisphosphate同工酶第一时间。困难的结构对新兴晶体学家们。

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