Division of Infectious Diseases, Department of Medicine, and Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO 63110, USA.
J Cell Sci. 2023 Mar 15;136(6). doi: 10.1242/jcs.260551. Epub 2023 Mar 6.
N-terminal acetylation is a common eukaryotic protein modification that involves the addition of an acetyl group to the N-terminus of a polypeptide. This modification is largely performed by cytosolic N-terminal acetyltransferases (NATs). Most associate with the ribosome, acetylating nascent polypeptides co-translationally. In the malaria parasite Plasmodium falciparum, exported effectors are thought to be translated into the endoplasmic reticulum (ER), processed by the aspartic protease plasmepsin V and then N-acetylated, despite having no clear access to cytosolic NATs. Here, we used inducible gene deletion and post-transcriptional knockdown to investigate the primary ER-resident NAT candidate, Pf3D7_1437000. We found that it localizes to the ER and is required for parasite growth. However, depletion of Pf3D7_1437000 had no effect on protein export or acetylation of the exported proteins HRP2 and HRP3. Despite this, Pf3D7_1437000 depletion impedes parasite development within the host red blood cell and prevents parasites from completing genome replication. Thus, this work provides further proof of N-terminal acetylation of secretory system proteins, a process unique to apicomplexan parasites, but strongly discounts a promising candidate for this post-translational modification.
N-端乙酰化是一种常见的真核蛋白修饰，涉及在多肽的 N 端添加乙酰基。这种修饰主要由胞质 N-端乙酰转移酶（NAT）完成。大多数与核糖体结合，共翻译乙酰化新生多肽。在疟原虫 Plasmodium falciparum 中，尽管没有明确的细胞质 NAT 进入途径，但认为分泌效应子被翻译到内质网（ER）中，被天冬氨酸蛋白酶 plasmepsin V 加工，然后进行 N-乙酰化。在这里，我们使用诱导型基因缺失和转录后敲低来研究主要的 ER 驻留 NAT 候选物 Pf3D7_1437000。我们发现它定位于 ER 中，是寄生虫生长所必需的。然而，Pf3D7_1437000 的耗竭对 HRP2 和 HRP3 等分泌蛋白的蛋白输出或乙酰化没有影响。尽管如此，Pf3D7_1437000 的耗竭会阻碍寄生虫在宿主红细胞内的发育，并阻止寄生虫完成基因组复制。因此，这项工作进一步证明了分泌系统蛋白的 N-端乙酰化，这是一种独特的质体寄生虫过程，但强烈否定了这种翻译后修饰的一个有希望的候选物。
