Cystatin C, also known as γ-trace or post-γ-globulin, is a cysteine protease inhibitor from the cystatin superfamily. It is usually used as a marker of the glomerular filtration rate owing to its low molecular weight and constant secretion. The recently available methods for cystatin C preparation have low outputs. Hence, a productive preparation system is urgently required. In this study, a 6 × His-tag coupled with a thrombin cleavage site was fused to the C-terminus of cystatin C, and the protein was well expressed in Escherichia coli after optimization. Then, two different systems were used to obtain no-tag cystatin C: a traditional nickel (Ni)-column system and a subtly Ni magnetic bead system. The column system was more commonly used, and the magnetic bead system was more convenient. Cystatin C (purity > 97%) was successfully obtained, and the yields in both the systems were higher than those in previous studies. Further, the proper folding status and bioactivity of recombinant cystatin C were confirmed using the papain inhibition assay, dynamic light scattering, and circular dichroism spectroscopy.

中文翻译：

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重组人胱抑素C的可溶性表达以及Ni柱和磁珠纯化的比较。

胱抑素C，也称为γ-迹线或γ-球蛋白后，是来自半胱氨酸蛋白酶抑制剂超家族的半胱氨酸蛋白酶抑制剂。由于它的低分子量和恒定的分泌，通常被用作肾小球滤过率的标志物。最近可用的制备半胱氨酸蛋白酶抑制剂C的方法产量低。因此，迫切需要生产准备系统。在这项研究中，将一个6×His-tag和一个凝血酶裂解位点融合到cystatin C的C末端，该蛋白在大肠杆菌中表达良好。经过优化。然后，使用两种不同的系统来获得无标签的胱抑素C：传统的镍（Ni）柱系统和微妙的镍磁珠系统。色谱柱系统更常用，磁珠系统更方便。成功获得了胱抑素C（纯度> 97％），两种系统的产率均高于以前的研究。此外，使用木瓜蛋白酶抑制分析，动态光散射和圆二色性光谱学证实了重组半胱氨酸蛋白酶抑制剂C的正确折叠状态和生物活性。