Structure of D-allose binding protein from Escherichia coli bound to D-allose at 1.8 Å resolution
Structure of D-allose binding protein from Escherichia coli bound to D-allose at 1.8 Å resolution
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DOI：
10.1006/jmbi.1999.2571
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发表时间：
1999-03-12
影响因子：
5.6
通讯作者：
Mowbray, SL
中科院分区：
文献类型：
--
作者：
Chaudhuri, BN;Ko, J;Mowbray, SL
ABC运输系统的输入或输出的营养物质和其他物质的细胞膜广泛分布在自然界中。在大多数细菌系统中，周质组分是整个转运复合物特异性的主要决定因素。我们在这里报告的晶体结构的周质结合蛋白的阿洛糖系统（ALBP）从大肠杆菌，解决了在1.8埃分辨率使用分子置换法。与该家族的其他成员（特别是核糖结合蛋白REP，与其具有35%的序列同源性）一样，该结构由两个由三链铰链区连接的相似结构域组成。蛋白质被认为在溶液中以封闭和开放构象的动态平衡存在，这是其功能的重要部分。在这里观察到的封闭配体结合形式中，D-阿洛糖被埋在结构域界面处。在晶体结构中仅观察到别吡喃糖的β-端基异构体，尽管α-端基异构体可以潜在地以类似的亲和力结合。配体结合裂缝的细节揭示了决定底物特异性的特征。广泛的氢键以及疏水相互作用被发现是重要的。来自两个结构域的总共10个残基与糖形成14个氢键。此外，三个芳环，每个结构域的一个芳环的表面平行于糖环的平面，第三个芳环垂直于糖环的平面，构成了环氢原子的疏水堆积表面。我们的研究结果表明，形成糖结合裂缝的芳环可以在空间上阻止任何己糖差向异构体的结合，除了D-阿洛糖，6-脱氧-阿洛糖或3-脱氧-葡萄糖;后两者预计结合亲和力降低，由于一些氢键的损失。戊糖的吡喃糖形式D-核糖也可以适合ALBP结合裂缝，尽管具有较低的结合亲和力。因此，ALBP可以作为D-核糖的低亲和力转运蛋白发挥作用。这些结果的意义进行了讨论的上下文中的阿洛糖和核糖运输系统的功能。(C)北京：科学出版社.
ABC transport systems for import or export of nutrients and other substances across the cell membrane are widely distributed in nature. In most bacterial systems, a periplasmic component is the primary determinant of specificity of the transport complex as a whole. We report here the crystal structure of the periplasmic binding protein for the allose system (ALBP) from Escherichia coli, solved at 1.8 Angstrom resolution using the molecular replacement method. As in the other members of the family (especially the ribose binding protein, REP, with which it shares 35% sequence homology), this structure consists of two similar domains joined by a three-stranded hinge region. The protein is believed to exist in a dynamic equilibrium of closed and open conformations in solution which is an important part of its function. In the closed ligand-bound form observed here, D-allose is buried at the domain interface. Only the beta-anomer of allopyranose is seen in the crystal structure, although the alpha-anomer can potentially bind with a similar affinity. Details of the ligand-binding cleft reveal the features that determine substrate specificity. Extensive hydrogen bonding as well as hydrophobic interactions are found to be important. Altogether ten residues from both the domains form 14 hydrogen bonds with the sugar. Ln addition, three aromatic rings, one from each domain with faces parallel to the plane of the sugar ring and a third perpendicular, make up a hydrophobic stacking surface for the ring hydrogen atoms. Our results indicate that the aromatic rings forming the sugar binding cleft can sterically block the binding of any hexose epimer except D-allose, 6-deoxy-allose or 3-deoxy-glucose; the latter two are expected to bind with reduced affinity, due to the loss of some hydrogen bonds. The pyranose form of the pentose, D-ribose, can also fit into the ALBP binding cleft, although with lower binding affinity. Thus, ALBP can function as a low affinity transporter for D-ribose. The significance of these results is discussed in the context of the function of allose and ribose transport systems. (C) 1999 Academic Press.