Chagas disease, which is caused by Trypanosoma cruzi, affects more than six million people worldwide. Cruzain is the major cysteine protease involved in the survival of this parasite. Here, the expression, purification and crystallization of this enzyme are reported. The cruzain crystals diffracted to 1.2 Å resolution, yielding two novel cruzain structures: apocruzain and cruzain bound to the reversible covalent inhibitor S‐methyl thiomethanesulfonate. Mass‐spectrometric experiments confirmed the presence of a methylthiol group attached to the catalytic cysteine. Comparison of these structures with previously published structures indicates the rigidity of the cruzain structure. These results provide further structural information about the enzyme and may help in new in silico studies to identify or optimize novel prototypes of cruzain inhibitors.

中文翻译：

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Cruzain结构：载脂蛋白和Cruzain与S-甲基硫代甲磺酸盐结合并影响药物设计。

克鲁格氏锥虫引起的恰加斯病，在全球范围内影响着600万人。Cruzain是参与此寄生虫生存的主要半胱氨酸蛋白酶。在此，报道了该酶的表达，纯化和结晶。克鲁萨因晶体衍射至1.2Å分辨率，产生了两个新颖的克鲁萨因结构：阿奇克鲁萨因和克鲁萨因与可逆共价抑制剂S-甲基硫代甲磺酸盐结合。质谱实验证实了存在于催化半胱氨酸上的甲硫醇基团。这些结构与先前公开的结构的比较表明了克鲁萨因结构的刚性。这些结果提供了有关酶的进一步结构信息，并可能有助于新的在计算机研究中鉴定或优化Cruzain抑制剂的新型原型。