Structures of purine nucleosidase from Trypanosoma brucei bound to isozyme-specific trypanocidals and a novel metalorganic inhibitor
Structures of purine nucleosidase from Trypanosoma brucei bound to isozyme-specific trypanocidals and a novel metalorganic inhibitor
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DOI：
10.1107/s0907444913010792
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发表时间：
2013-08-01
期刊：
影响因子：
--
通讯作者：
Degano, Massimo
中科院分区：
文献类型：
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作者：
Giannese, Francesca;Berg, Maya;Degano, Massimo
昏睡病是一种致命的疾病，主要影响撒哈拉以南非洲地区，由锥虫属的原生动物寄生虫引起。锥虫是嘌呤营养缺陷型，其摄取途径一直被认为是药物设计的有吸引力的靶标。最近，锥虫嘌呤特异性核苷水解酶（IAGNH）的一种紧密结合的竞争性抑制剂在小鼠感染模型中显示出显着的杀锥虫活性。在这里，T.本发明提供了布氏杆菌IAGNH，以及其未配体形式和与不同抑制剂（包括杀锥虫化合物UAMC-00363）的复合物的高分辨率结构。说明的关键接触，占高亲和力抑制IAGNH亚氨基核糖基化合物的描述和酶催化所需的构象变化的分子机制被确定。首次证明了金属有机配合物可以在核苷水解酶的活性位点竞争结合，模仿酶促反应的带正电荷的过渡态。此外，我们表明，二价金属离子可以作为非竞争性IAGNH抑制剂，稳定的催化环的非生产性构象。这些结果为合理改善现有化合物的效力和选择性开辟了一条道路，并提出了可用作新型抗锥虫化合物设计蓝图的新支架。
Sleeping sickness is a deadly disease that primarily affects sub-Saharan Africa and is caused by protozoan parasites of the Trypanosoma genus. Trypanosomes are purine auxotrophs and their uptake pathway has long been appreciated as an attractive target for drug design. Recently, one tight-binding competitive inhibitor of the trypanosomal purine-specific nucleoside hydrolase (IAGNH) showed remarkable trypanocidal activity in a murine model of infection. Here, the enzymatic characterization of T. brucei brucei IAGNH is presented, together with its high-resolution structures in the unliganded form and in complexes with different inhibitors, including the trypanocidal compound UAMC-00363. A description of the crucial contacts that account for the high-affinity inhibition of IAGNH by iminoribitol-based compounds is provided and the molecular mechanism underlying the conformational change necessary for enzymatic catalysis is identified. It is demonstrated for the first time that metalorganic complexes can compete for binding at the active site of nucleoside hydrolase enzymes, mimicking the positively charged transition state of the enzymatic reaction. Moreover, we show that divalent metal ions can act as noncompetitive IAGNH inhibitors, stabilizing a nonproductive conformation of the catalytic loop. These results open a path for rational improvement of the potency and the selectivity of existing compounds and suggest new scaffolds that may be used as blueprints for the design of novel antitrypanosomal compounds.