Sudo Atsushi, Kato Kentaro, Kobayashi Kyousuke, Tohya Yukinobu, Akashi Hiroomi
Department of Veterinary Microbiology, Faculty of Agriculture, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Japan.
Mol Biochem Parasitol. 2008 Aug;160(2):138-42. doi: 10.1016/j.molbiopara.2008.03.011. Epub 2008 Apr 16.
Cyclic AMP-dependent protein kinase (protein kinase A, PKA) is a key element in many cell signaling pathways. An essential role of Plasmodium falciparum PKA (PfPKA) activity was reported in the intraerythrocytic growth of the malaria parasite. However, molecular characterization of PfPKA using purified recombinant proteins has not yet been performed. Here, we report the first successful purification of the enzymatically active PKA catalytic subunit of P. falciparum (PfPKA-C) using a wheat germ cell-free expression system. Interestingly, parasite enzymatic activity was weakly inhibited as compared with the inhibition of mammalian PKA catalytic subunit (PKA-C) by the specific PKA inhibitor, H89. Furthermore, PfPKA-C was only slightly inhibited by protein kinase inhibitor (PKI). These results suggest that substrate sites of PfPKA-C may be different from those of mammalian PKA-Cs. In addition, potential PKI corresponding to malarial PKA-C would also be different from those of mammalian cells.
环磷酸腺苷依赖性蛋白激酶（蛋白激酶A，PKA）是许多细胞信号通路中的关键要素。据报道，恶性疟原虫PKA（PfPKA）活性在疟原虫红细胞内生长过程中发挥着重要作用。然而，尚未使用纯化的重组蛋白对PfPKA进行分子表征。在此，我们报道了首次使用小麦胚无细胞表达系统成功纯化出具有酶活性的恶性疟原虫PKA催化亚基（PfPKA-C）。有趣的是，与特异性PKA抑制剂H89对哺乳动物PKA催化亚基（PKA-C）的抑制作用相比，疟原虫的酶活性受到的抑制较弱。此外，PfPKA-C仅受到蛋白激酶抑制剂（PKI）的轻微抑制。这些结果表明，PfPKA-C的底物位点可能与哺乳动物PKA-C的底物位点不同。此外，与疟原虫PKA-C相对应的潜在PKI也可能与哺乳动物细胞的不同。
