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首页> 外文期刊>Journal of Molecular Biology >The 'Open' and 'Closed' structures of the type-C inorganic pyrophosphatases from Bacillus subtilis and Streptococcus gordonii
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The 'Open' and 'Closed' structures of the type-C inorganic pyrophosphatases from Bacillus subtilis and Streptococcus gordonii

机译：枯草芽孢杆菌和戈登链球菌的C型无机焦磷酸酶的“开放”和“封闭”结构

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摘要

Recently, a new class of soluble inorganic pyrophosphatase (type-C PPase) has been described that is not homologous in amino acid sequence or kinetic properties to the well-studied PPases (types A and B) found in many organisms from bacteria to humans and thought to be essential to the cell. Structural studies of the type-C PPases from Streptococcus gordonii and Bacillus subtilis reveal a homodimeric structure, with each polypeptide folding into two domains joined by a flexible hinge. The active site, formed at the interface between the N and C-terminal domains, binds two manganese ions approximately 3.6 Angstrom apart in a conformation resembling binuclear metal centres found in other hydrolytic enzymes. An activated water molecule bridging the two metal ions is likely poised for nucleophilic attack of the substrate. Importantly, the S. gordonii and B. subtilis enzymes have crystallised in strikingly different conformations. In both subunits of the S. gordonii crystal structure (1.5 Angstrom resolution) the C-terminal domain is positioned such that the active site is occluded, with a sulphate ion bound in the active site. In contrast, in the B. subtilis structure (3.0 Angstrom resolution) the C-terminal domain is rotated by about 90 degrees, leaving the active site wide open and accessible for substrate binding.
机译：最近，已经描述了一类新的可溶性无机焦磷酸酶（C型PPase），其氨基酸序列或动力学特性与从细菌到人类以及许多生物体中发现的许多经过研究的PPase（A和B型）均不同源。被认为对细胞至关重要。来自戈登链球菌和枯草芽孢杆菌的C型PPase的结构研究显示同型二聚体结构，每个多肽折叠成两个域，并通过柔性铰链连接。在N和C末端结构域之间的界面处形成的活性位点，以类似于其他水解酶中发现的双核金属中心的构型结合两个相距约3.6埃的锰离子。桥接两个金属离子的活化水分子很可能蓄势于底物的亲核攻击。重要的是，戈登氏链球菌和枯草芽孢杆菌的酶以明显不同的构象结晶。在戈氏链球菌晶体结构的两个亚基（分辨率为1.5埃）中，C末端结构域的位置应使活性位点被封闭，且硫酸根离子键合在活性位点中。相反，在枯草芽孢杆菌结构（分辨率为3.0埃）中，C末端结构域旋转了大约90度，使活性位点敞开并易于与底物结合。

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