Antifolate-resistant mutants of Plasmodium falciparum dihydrofolate reductase
Antifolate-resistant mutants of Plasmodium falciparum dihydrofolate reductase
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DOI：
10.1073/pnas.94.4.1124
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发表时间：
1997-02-18
影响因子：
11.1
通讯作者：
Santi, DV
中科院分区：
文献类型：
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作者：
Sirawaraporn, W;Sathitkul, T;Santi, DV
恶性疟原虫二氢叶酸还原酶(PfDHFR)第16、51、59、108和164位的单个和多个突变与疟疾的抗叶酸耐药性有关。我们制备并鉴定了自然界中发现的所有7个pfDHFR突变体以及6个未在自然界中观察到的突变体，涉及51、59、108或164残基的突变对抗叶酸乙胺胺和环鸟苷具有交叉抗性，而残基16的突变则对环鸟苷具有特异性抗药性。自然界中发现的酶突变体的抗叶酸抗性与体内的抗叶酸抗性相关；然而，自然界中未发现的突变体要么抗性较差，要么催化活性不足以支持DNA合成，因此，自然界中选择了靶残基上多个突变的特定组合来优化抗药性，而且多个突变体的抗药性大于组分单个突变的总和，这表明选择残基是因为它们之间的协同作用和对抗性的内在影响，推测乙胺胺抗性突变体的进化途径表明，所有多个突变体都是通过对单个突变体S108N的逐步选择而产生的，因此，我们认为针对野生型pfDHFR和S108N突变体的药物产生耐药性的可能性很低。因此可以提供有效的抗疟疾药物。
Single and multiple mutations at residues 16, 51, 59, 108, and 164 of Plasmodium falciparum dihydrofolate reductase (pfDHFR) have been linked to antifolate resistance in malaria. We prepared and characterized all seven of the pfDHFR mutants found in nature, as well as six mutants not observed in nature, Mutations involving residues 51, 59, 108, or 164 conferred cross resistance to both the antifolates pyrimethamine and cycloguanil, whereas mutation of residue 16 specifically conferred resistance to cycloguanil. The antifolate resistance of enzyme mutants found in nature correlated with in vivo antifolate resistance; however, mutants not found in nature were either poorly resistant or had insufficient catalytic activity to support DNA synthesis, Thus, specific combinations of multiple mutations at target residues were selected in nature to optimize resistance, Further, the resistance of multiple mutants was more than the sum of the component single mutations, indicating that residues were selected for their synergistic as well as intrinsic effects on resistance, Pathways inferred for the evolution of pyrimethamine-resistant mutants suggested that all multiple mutants emerged from stepwise selection of the single mutant, S108N, Thus, we propose that drugs targeted to both the wild-type pfDHFR and S108N mutant would have a low propensity for developing resistance, and hence could provide effective antimalarial agents.