Sharma Sutikshan, Pradhan Arun, Chauhan Virander S, Tuteja Renu
Malaria Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
J Biomed Biotechnol. 2005;2005(4):301-9. doi: 10.1155/JBB.2005.301.
Type I signal peptidases are important membrane-bound serine proteases responsible for the cleavage of the signal peptide of the proteins. These enzymes are unique serine proteases that carry out catalysis using a serine/lysine catalytic dyad. In the present study, we report the isolation of type I signal peptidase from the malaria parasites Plasmodium falciparum, Plasmodium knowlesi, and Plasmodium yoelii and some characterization of type I signal peptidase of Plasmodium falciparum. We show that these enzymes are homologous to signal peptidases from various sources and also contain the conserved boxes present in other type I signal peptidases. The type I signal peptidase from P falciparum is an intron-less and a single-copy gene. The results also show that the enzyme from Plasmodium falciparum is subject to self-cleavage and it has been demonstrated to possess type I signal peptidase activity in E coli preprotein processing in vivo by complementation assay. This study will be helpful in understanding one of the important metabolic pathways "the secretory pathway" in the parasite and should make an important contribution in understanding the complex process of protein targeting in the parasite.
I型信号肽酶是重要的膜结合丝氨酸蛋白酶，负责切割蛋白质的信号肽。这些酶是独特的丝氨酸蛋白酶，利用丝氨酸/赖氨酸催化二元体进行催化。在本研究中，我们报告了从恶性疟原虫、诺氏疟原虫和约氏疟原虫中分离出I型信号肽酶，并对恶性疟原虫的I型信号肽酶进行了一些特性分析。我们表明，这些酶与来自各种来源的信号肽酶同源，并且还含有其他I型信号肽酶中存在的保守框。恶性疟原虫的I型信号肽酶是一个无内含子的单拷贝基因。结果还表明，来自恶性疟原虫的酶会发生自我切割，并且通过互补试验已证明其在体内大肠杆菌前体蛋白加工中具有I型信号肽酶活性。这项研究将有助于理解寄生虫中重要的代谢途径之一“分泌途径”，并应为理解寄生虫中蛋白质靶向的复杂过程做出重要贡献。
