Characterization of a novel serine/threonine protein phosphatase (PfPPJ) from the malaria parasite, Plasmodium falciparum
Characterization of a novel serine/threonine protein phosphatase (PfPPJ) from the malaria parasite, Plasmodium falciparum
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DOI：
10.1016/s0166-6851(01)00260-2
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发表时间：
2001-06-01
影响因子：
1.5
通讯作者：
Barik, S
中科院分区：
文献类型：
--
作者：
Dobson, S;Bracchi, V;Barik, S
从恶性疟原虫（Plasmodium falciparum，Pf）中鉴定出一个新的PPP超家族蛋白磷酸酶cDNA，暂命名为PfPPJ。预测的磷酸酶的一级结构包含所有已知的PPP超家族的催化活性所必需的保守基序。该酶对磷酸丝氨酸和磷酸苏氨酸残基的去磷酸化具有特异性，对磷酸酪氨酸残基的活性非常小。然而，其C-末端的序列是独特的，并且与其对经典的PP 2A特异性抑制剂如冈田酸和微囊藻毒素-LR以及PPI特异性抑制剂哺乳动物热稳定抑制剂-2（I-2）的抗性一致。甚至PfPPJ的催化核心也具有与其他PPP显著不同的序列，使得PfPPJ可以被置于明显独立的系统发育分支中。在294个氨基酸残基，PfPPJ是已知的最小的抗冈田酸PPP磷酸酶之一。通过北方印迹分析，PfPPJ mRNA的表达呈现以下模式：鞭毛>环>滋养体，这与免疫荧光检测的蛋白表达密切相关。总之，这些结果表明寄生阶段特异性转录调节这种新的和潜在的独特的原生动物磷酸酶。(C)2001 Elsevier Science B. V.保留所有权利。
A novel protein phosphatase cDNA of the PPP superfamily was identified from the malaria parasite, Plasmodium falciparum (Pf), and tentatively named PfPPJ. The predicted primary structure of the phosphatase contained all the known conserved motifs of the PPP superfamily essential for catalytic activity. The enzyme was specific for dephosphorylation of phosphoserine and phosphothreonine residues with very little activity against phosphotyrosine residues. However, the sequence at its C-terminal end was unique, and was consistent with its resistance to the classical PP2A-specific inhibitors such as okadaic acid and microcystin-LR, and the PPI-specific inhibitor, mammalian heat-stable inhibitor-2 (I-2). Even the catalytic core of PfPPJ had a sequence substantially different from the other PPPs such that PfPPJ could be placed in an apparently separate phylogenetic branch. At 294 amino acids residues, PfPPJ was one of the smallest okadaic acid-resistant PPP phosphatases known. By Northern blot analysis, the expression of the PfPPJ mRNA showed the following pattern: schizont > ring > trophozoite, which closely paralleled the expression of the protein, as determined by immunofluorescence. Together, these results suggested a parasitic stage-specific transcriptional regulation of this novel and potentially unique protozoan phosphatase. (C) 2001 Elsevier Science B.V. All rights reserved.