Identification and stoichiometry of glycosylphosphatidylinositol-anchored membrane proteins of the human malaria parasite Plasmodium falciparum
Identification and stoichiometry of glycosylphosphatidylinositol-anchored membrane proteins of the human malaria parasite Plasmodium falciparum
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DOI：
10.1074/mcp.m600035-mcp200
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发表时间：
2006-07-01
影响因子：
7
通讯作者：
Crabb, Brendan S.
中科院分区：
文献类型：
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作者：
Gilson, Paul R.;Nebl, Thomas;Crabb, Brendan S.
大多数覆盖在人类疟疾寄生虫恶性疟原虫胞外形式表面的蛋白质通过糖基磷脂酰肌醇(GPI)锚点附着在质膜上。这些蛋白质与中和抗体接触，其中几种是先进的候选疫苗。为了鉴定恶性疟原虫GPI锚定的蛋白质组，我们结合了蛋白质组学和计算方法。针对生命周期中与临床相关的血液阶段，用放射性氨基葡萄糖标记的蛋白质组学分析表明，GPI锚定在11个蛋白质上(裂殖子表面蛋白(MSP)-1、-2、-4、-5、-10、棒状病毒相关膜抗原、顶端寿司蛋白、Pf92、Pf38、Pf12和Pf34)。这些蛋白质与GPI锚定的裂殖体/裂殖子蛋白质组的94%相似，构成了迄今为止该生物体中最大的一组GPI锚定蛋白质。此外，MSP-1和MSP-2以相似的拷贝数存在，我们估计这些蛋白加在一起约占膜相关表面涂层总数的三分之二。这是第一次对微晶石粉的化学计量进行检测。我们观察到，现有的软件在预测锚定在恶性疟原虫蛋白上的GPI方面表现不佳，而这种修改已被蛋白质组学验证。因此，我们开发了一个针对恶性疟原虫序列的隐马尔可夫模型(GPI-HMM)，并使用该模型根据GPI锚定的可能性对完整的恶性疟原虫基因组中编码的所有蛋白质进行排序。GPI-HMM预测了在所有已验证的蛋白质、几个已知的膜蛋白以及一些可能在血液、昆虫和/或红细胞前阶段生命周期中表达的新的表面蛋白质上的GPI修饰。这项工作在恶性疟原虫中总共鉴定了11个蛋白，并预测了另外19个GPI锚定蛋白。
Most proteins that coat the surface of the extracellular forms of the human malaria parasite Plasmodium falciparum are attached to the plasma membrane via glycosylphosphatidylinositol (GPI) anchors. These proteins are exposed to neutralizing antibodies, and several are advanced vaccine candidates. To identify the GPI-anchored proteome of P. falciparum we used a combination of proteomic and computational approaches. Focusing on the clinically relevant blood stage of the life cycle, proteomic analysis of proteins labeled with radioactive glucosamine identified GPI anchoring on 11 proteins (merozoite surface protein (MSP)-1, -2, -4, -5, -10, rhoptry-associated membrane antigen, apical sushi protein, Pf92, Pf38, Pf12, and Pf34). These proteins represent similar to 94% of the GPI-anchored schizont/merozoite proteome and constitute by far the largest validated set of GPI-anchored proteins in this organism. Moreover MSP-1 and MSP- 2 were present in similar copy number, and we estimated that together these proteins comprise approximately two-thirds of the total membrane-associated surface coat. This is the first time the stoichiometry of MSPs has been examined. We observed that available software performed poorly in predicting GPI anchoring on P. falciparum proteins where such modification had been validated by proteomics. Therefore, we developed a hidden Markov model (GPI-HMM) trained on P. falciparum sequences and used this to rank all proteins encoded in the completed P. falciparum genome according to their likelihood of being GPI-anchored. GPI-HMM predicted GPI modification on all validated proteins, on several known membrane proteins, and on a number of novel, presumably surface, proteins expressed in the blood, insect, and/or pre-erythrocytic stages of the life cycle. Together this work identified 11 and predicted a further 19 GPI-anchored proteins in P. falciparum.