Preliminary X-ray analysis of a new crystal form of the Escherichia coli KDO8P synthase.
Preliminary X-ray analysis of a new crystal form of the Escherichia coli KDO8P synthase.
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DOI：
10.1107/s0907444900002389
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发表时间：
2000-04
期刊：
影响因子：
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通讯作者：
S. Radaev;P. Dastidar;M. Patel;R. Woodard;D. Gatti
中科院分区：
文献类型：
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作者：
S. Radaev;P. Dastidar;M. Patel;R. Woodard;D. Gatti
3-脱氧-D-甘露-辛酮糖酸8-磷酸（KDO 8 P）合酶催化所有革兰氏阴性细菌的脂多糖的必需组分的生物合成。KDO 8 P合酶的结构和机制正在积极研究，因为这种酶代表了抗生素治疗的重要靶标。大肠杆菌KDO 8 P合成酶的立方晶体（空间群I23）的结构最近已被确定，该酶被证明是一个四聚体的相同的亚基。然而，这一信息受到生物化学研究的挑战，这表明该酶在溶液中表现为同源三聚体。本文报道了KDO 8 P合成酶单斜晶体的制备和初步X射线分析。晶体属于空间群P2（1），晶胞参数a约为50，B约为140，c约为74，β约为105度。单斜晶体形式的KDO 8 P合酶的结构通过分子置换确定，使用立方晶体中的酶的亚基之一作为搜索模型。具有222局部对称性的KDO 8 P合酶的四聚体也存在于P2（1）晶体的不对称单元中，溶剂含量为43%。在属于不同晶体系统（单斜晶系和立方晶系）的两种不同晶体形式中观察到KDO 8 P合酶的相同四级结构的观察结果表明四聚体是酶的天然形式。
3-Deoxy-D-manno-octulosonate 8-phosphate (KDO8P) synthase catalyzes the biosynthesis of an essential component of the lipopolysaccharide of all Gram-negative bacteria. The structure and mechanism of KDO8P synthase are being actively studied as this enzyme represents an important target for antibiotic therapy. The structure of the Escherichia coli KDO8P synthase in cubic crystals (space group I23) has recently been determined and the enzyme shown to be a tetramer of identical subunits. However, this information is challenged by biochemical studies, which suggest that the enzyme behaves in solution as a homotrimer. Here, the preparation and preliminary X-ray analysis of monoclinic crystals of KDO8P synthase are reported. The crystals belong to space group P2(1), with unit-cell parameters a approximately 50, b approximately 140, c approximately 74 A, beta approximately 105 degrees. The structure of KDO8P synthase in the monoclinic crystal form was determined by molecular replacement, using as a search model one of the subunits of the enzyme in the cubic crystals. A tetramer of KDO8P synthase with 222 local symmetry is also present in the asymmetric unit of the P2(1) crystals, with a solvent content of 43%. The observation that the same quaternary structure of KDO8P synthase is observed in two different crystal forms belonging to distinct crystal systems (monoclinic and cubic) suggests that a tetramer is the native form of the enzyme.