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首页> 外文期刊>Biochemistry >Crystal structures of a unique thermal-stable thymidylate synthase from Bacillus subtilis
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Crystal structures of a unique thermal-stable thymidylate synthase from Bacillus subtilis

机译：枯草芽孢杆菌独特的热稳定胸苷酸合酶的晶体结构

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Unlike all other organisms studied to date, Bacillus subtilis expresses two different thymidylate synthases: bsTS-A and bsTS-B. bsTS-A displays enhanced enzymatic and structural thermal stability uncharacteristic of most TSs, Despite the high level of TS conservation across most species, bsTS-A shares low sequence identity (<40%) with the majority of TSs from other organisms. This TS and the TSs from Lactococcus lactis and phage Phi 3T-to which it is most similar-have been of interest for some time since, by structure-based sequence alignment, they appear to lack several key residues shown by mutagenesis to be essential to enzymatic function [Greene, P. J., Yu, P. L., Zhao, J,, Schiffer, C, A., and Santi, D, (1994) Protein Sci. 3, 1114-6]. In addition, bsTS-A demonstrates specific activity 2-3-fold higher than TS from Lactobacillus casei or Escherichia coli. We have solved the crystal structure of this unusual TS in four crystal forms to a maximum resolution of 1.7 BL Each of these crystal forms contains either one or two noncrystallographically related dimers, Stabilization of the beta-sheet dimer interface through a dramatic architecture of buttressed internal salt bridges maintains the structural integrity of bsTS-A at elevated temperatures. Melting curves of TSs from L, casei and E. coli are compared to that of TS-A from B. subtilis and correlated with numbers of hydrogen bonds, salt bridges, and the numbers of interactions localized to the dimer interface. Analysis of this structure will shed light on the conservation of function across diversity of sequence, as well as provide insights into the thermal stabilization of a highly conserved enzyme. [References: 44]
机译：与迄今研究的所有其他生物不同，枯草芽孢杆菌表达两种不同的胸苷酸合酶：bsTS-A和bsTS-B。尽管大多数物种中TS的保守程度很高，但bsTS-A显示出增强的酶和结构热稳定性，这与大多数TS的特性不同，但bsTS-A与来自其他生物的大多数TS共有较低的序列同一性（<40％）。该TS和与乳酸乳球菌和噬菌体Phi 3T最相似的TS引起了人们的关注一段时间，因为通过基于结构的序列比对，它们似乎缺乏诱变显示出的几个关键残基对于酶功能[Greene，PJ，Yu，PL，Zhao，J，Schiffer，C，A。，和Santi，D，（1994）Protein Sci.Biol.215：403-10。 3，1114-6]。另外，bsTS-A显示出比干酪乳杆菌或大肠杆菌的TS高2-3倍的比活性。我们已经解决了这种不寻常的TS的四种晶体形式的晶体结构，最大分辨率为1.7 BL。这些晶体形式均包含一个或两个与非晶体学相关的二聚体，通过戏剧性的支撑内部结构来稳定β-sheet二聚体界面盐桥在高温下可保持bsTS-A的结构完整性。将来自L，酪蛋白和大肠杆菌的TS的熔解曲线与来自枯草芽孢杆菌的TS-A的熔解曲线进行了比较，并与氢键，盐桥的数量以及位于二聚体界面上的相互作用的数量相关。对这种结构的分析将揭示跨序列多样性的功能保守性，并提供对高度保守的酶的热稳定性的见解。 [参考：44]

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