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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Structure of dNTP-inducible dNTP triphosphohydrolase: insight into broad specificity for dNTPs and triphosphohydrolase-type hydrolysis
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Structure of dNTP-inducible dNTP triphosphohydrolase: insight into broad specificity for dNTPs and triphosphohydrolase-type hydrolysis

机译：结构dNTP-inducible核苷酸triphosphohydrolase:深入广泛核苷酸特异性和triphosphohydrolase-type水解

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摘要

Deoxyribonucleoside triphosphate triphosphohydrolase from Thermus thermophilus (Tt-dNTPase) has a unique regulatory mechanism for the degradation of deoxyribonucleoside triphosphates (dNTPs). Whereas the Escherichia coli homologue specifically hydrolyzes dGTP alone, dNTPs act as both substrate and activator for Tt-dNTPase. Here, the crystal structure of Tt-dNTPase has been determined at 2.2 angstrom resolution, representing the first report of the tertiary structure of a dNTPase homologue belonging to the HD superfamily, a diverse group of metal-dependent phosphohydrolases that includes a variety of uncharacterized proteins. This enzyme forms a homohexamer as a double ring of trimers. The subunit is composed of 19 alpha-helices; the inner six helices include the region annotated as the catalytic domain of the HD superfamily. Structural comparison with other HD-superfamily proteins indicates that a pocket at the centre of the inner six helices, formed from highly conserved charged residues clustered around a bound magnesium ion, constitutes the catalytic site. Tt-dNTPase also hydrolyzed noncanonical dNTPs, but hardly hydrolyzed dNDP and dNMP. The broad substrate specificity for different dNTPs might be rationalized by the involvement of a flexible loop during molecular recognition of the base moiety. Recognition of the triphosphate moiety crucial for the activity might be attained by highly conserved positively charged residues. The possible mode of dNTP binding is discussed in light of the structure.
机译：脱氧核苷三磷酸从栖热菌属triphosphohydrolase酸奶(Tt-dNTPase)有一个独特的监管机制脱氧核苷的降解三磷酸腺苷(核苷酸)。专门水解dGTP杆菌同系物孤独,核苷酸作为基质和激活Tt-dNTPase。Tt-dNTPase已经确定为2.2埃分辨率,代表的第一个报告dNTPase同系物的三级结构属于高清总科,一个多样化的组的metal-dependent phosphohydrolases,包括各种无特征的蛋白质。这种酶形式homohexamer作为双戒指三。阿尔法螺旋;注释的催化域高清总科。HD-superfamily蛋白质表明一个口袋里内六螺旋的中心,形成了从高度保守的残留集群围绕一个镁离子,构成了催化部位。典中的核苷酸,但几乎没有水解dNDP和dNMP。不同的核苷酸可能是合理的在分子的参与一个灵活的循环一部分识别的基础。三磷酸的一部分活动的关键可能达到的高度保守的积极带电残基。绑定是讨论的结构。

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