Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, usa.
Antimicrob Agents Chemother. 2010 Apr;54(4):1453-60. doi: 10.1128/AAC.01150-09. Epub 2010 Feb 9.
The human parasite Toxoplasma gondii is sensitive to dinitroaniline compounds which selectively disrupt microtubules in diverse protozoa but which have no detectable effect on vertebrate host cell microtubules or other functions. Replication of wild-type T. gondii is inhibited by 0.5 to 2.5 microM oryzalin, but mutant parasites harboring amino acid substitutions in the predicted dinitroaniline binding site confer resistance up to 40 microM oryzalin. However, the precise interaction between dinitroanilines and the binding site in alpha-tubulin remains unclear. We have investigated the activity of 12 dinitroanilines and the related compound amiprophos methyl on wild-type and dinitroaniline-resistant parasite lines that contain proposed binding site mutations. These data indicate that dinitramine is the most effective dinitroaniline to inhibit Toxoplasma growth in wild-type parasites and most resistant lines. Dinitramine has an amine group at the meta position not present in any of the other dinitroanilines tested here that is predicted to form hydrogen bonds with residues Arg2 and Gln133 according to docking data. Remarkably, although the binding site mutation Ile235Val confers increased resistance to most dinitroanilines, it confers increased sensitivity to GB-II-5, a compound optimized for activity against kinetoplastid tubulin. Kinetoplastid parasites have a valine at position 235 of alpha-tubulin, whereas apicomplexan parasites have an isoleucine at this site. We suggest that this heterogeneity in binding site environment influences relative dinitroaniline sensitivity in distinct protozoan lineages and hypothesize that a mutation that makes the apicomplexan dinitroaniline binding site more like the kinetoplastid site increases sensitivity to a dinitroaniline optimized for activity in the latter parasites.
刚地弓形虫是一种人体寄生虫，对二硝基苯胺类化合物敏感，这类化合物选择性地破坏各种原生动物的微管，但对脊椎动物宿主细胞的微管或其他功能没有明显影响。野生型刚地弓形虫的复制被 0.5 到 2.5μM 的氧氮宾抑制，但携带预测的二硝基苯胺结合部位氨基酸取代的突变寄生虫对高达 40μM 的氧氮宾具有抗性。然而，二硝基苯胺与α-微管蛋白结合部位的确切相互作用仍不清楚。我们研究了 12 种二硝基苯胺和相关化合物氨丙磷甲基对含有预测结合部位突变的野生型和二硝基苯胺抗性寄生虫系的活性。这些数据表明，二硝甲胺是抑制野生型寄生虫和大多数抗性系中弓形虫生长最有效的二硝基苯胺。二硝甲胺在间位有一个氨基，在我们这里测试的其他二硝基苯胺中都没有，根据对接数据，这个氨基预测与残基 Arg2 和 Gln133 形成氢键。值得注意的是，尽管结合部位突变 Ile235Val 赋予了对大多数二硝基苯胺的更高抗性，但它赋予了对 GB-II-5 的更高敏感性，GB-II-5 是一种针对动基体微管优化的化合物。动基体寄生虫在α-微管的 235 位有缬氨酸，而顶复门寄生虫在这个位置有异亮氨酸。我们认为，结合部位环境的这种异质性会影响不同原生动物谱系中二硝基苯胺的相对敏感性，并假设使顶复门二硝基苯胺结合部位更类似于动基体部位的突变会增加对针对后者寄生虫优化活性的二硝基苯胺的敏感性。
