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首页> 外文期刊>Biochimica et biophysica acta: BBA: International journal of biochemistry, biophysics and molecular biololgy. Proteins and Proteomics >Effect of NaCl on the conformational stability of the thermophilic ??-glutamyltranspeptidase from Geobacillus thermodenitrificans: Implication for globular protein halotolerance
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Effect of NaCl on the conformational stability of the thermophilic ??-glutamyltranspeptidase from Geobacillus thermodenitrificans: Implication for globular protein halotolerance

机译：NaCl对热树突孢嗜热芽孢杆菌嗜热性β-谷氨酰转肽酶构象稳定性的影响：对球蛋白耐盐性的影响。

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摘要

The transpeptidation activity of ??-glutamyltranspeptidase from Geobacillus thermodenitrificans (GthGT) is negligible and the enzyme is highly thermostable. Here we have examined the effect of concentrated NaCl solutions on structure, stability, dynamics and enzymatic activity of GthGT. The protein exhibited hydrolytic activity over a broad range of NaCl concentrations. Even at 4.0 M NaCl, GthGT retained more than 90% of the initial activity and showed unaltered fluorescence emission, secondary structure and acrylamide quenching on tryptophan fluorescence. Furthermore, at 2.8 M and 4.0 M NaCl the temperature-induced unfolding profiles are dramatically changed with large (> 20 ??C) positive shifts in the denaturation temperature. These features make GthGT an ideal system to be used in industrial processes that require high temperatures and high-salt environments. A general explanation of the NaCl effect by means of a statistical thermodynamic model is also provided, together with an analysis of residue distribution between protein surface and interior in 15 non-redundant families of halophilic and non-halophilic proteins. The results are in line with a comparative sequence and structural analysis between halophilic and non-halophilic ??-glutamyltranspeptidases which revealed that a major role in halotolerance should be played by solvent exposed negatively charged residues. ? 2012 Elsevier B.V. All rights reserved.
机译：来自热树芽孢杆菌（GthGT）的β-谷氨酰转肽酶的转肽活性可以忽略不计，并且该酶是高度热稳定的。在这里，我们检查了浓NaCl溶液对GthGT的结构，稳定性，动力学和酶活性的影响。该蛋白质在很宽的NaCl浓度范围内均表现出水解活性。即使在4.0 M NaCl中，GthGT仍保留了超过90％的初始活性，并在色氨酸荧光上显示出不变的荧光发射，二级结构和丙烯酰胺猝灭。此外，在2.8 M和4.0 M NaCl下，随着变性温度的大（> 20°C）正移，温度引起的展开曲线显着变化。这些功能使GthGT成为需要高温和高盐环境的工业过程中使用的理想系统。还提供了通过统计热力学模型对NaCl效应的一般解释，并分析了15个非冗余和非嗜盐蛋白家族中蛋白质表面和内部之间的残基分布。该结果与嗜盐和非嗜盐的β-谷氨酰转肽酶之间的比较序列和结构分析相符，该分析揭示了在耐盐性中的主要作用应该是溶剂暴露于负电荷的残基。 ？ 2012 Elsevier B.V.保留所有权利。

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