Pachebat Justin A, Kadekoppala Madhusudan, Grainger Munira, Dluzewski Anton R, Gunaratne Ruwani S, Scott-Finnigan Terence J, Ogun Solabomi A, Ling Irene T, Bannister Lawrence H, Taylor Helen M, Mitchell Graham H, Holder Anthony A
Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London NW1 1AA, UK.
Mol Biochem Parasitol. 2007 Jan;151(1):59-69. doi: 10.1016/j.molbiopara.2006.10.006. Epub 2006 Nov 2.
In Plasmodium falciparum, merozoite surface protein 7 (MSP7) was originally identified as a 22kDa protein on the merozoite surface and associated with the MSP1 complex shed during erythrocyte invasion. MSP7 is synthesised in schizonts as a 351-amino acid precursor that undergoes proteolytic processing. During biosynthesis the MSP1 and MSP7 precursors form a complex that is targeted to the surface of developing merozoites. In the sequential proteolytic processing of MSP7, N- and C-terminal 20 and 33kDa products of primary processing, MSP7(20) and MSP7(33) are formed and MSP7(33) remains bound to full length MSP1. Later in the mature schizont, MSP7(20) disappears from the merozoite surface and on merozoite release MSP7(33) undergoes a secondary cleavage yielding the 22kDa MSP7(22) associated with MSP1. In free merozoites, both MSP7(22) and a further cleaved product, MSP7(19) present only in some parasite lines, were detected; these two derivatives are shed as part of the protein complex with MSP1 fragments during erythrocyte invasion. Primary processing of MSP7 is brefeldin A-sensitive while secondary processing is resistant to both calcium chelators and serine protease inhibitors. Primary processing of MSP7 occurs prior to that of MSP1 in a post-Golgi compartment, whereas the secondary cleavage occurs on the surface of the developing merozoite, possibly at the time of MSP1 primary processing and well before the secondary processing of MSP1.
在恶性疟原虫中，裂殖子表面蛋白7（MSP7）最初被鉴定为裂殖子表面上的一种22kDa蛋白，并且与红细胞入侵期间脱落的MSP1复合物相关。MSP7在裂殖体中作为一种351个氨基酸的前体合成，该前体经过蛋白水解加工。在生物合成过程中，MSP1和MSP7前体形成一个复合物，该复合物靶向发育中的裂殖子表面。在MSP7的顺序蛋白水解加工过程中，形成了初级加工的N端和C端20kDa和33kDa产物，即MSP7(20)和MSP7(33)，并且MSP7(33)仍然与全长MSP1结合。在成熟裂殖体后期，MSP7(20)从裂殖子表面消失，并且在裂殖子释放时，MSP7(33)经历二次切割，产生与MSP1相关的22kDa MSP7(22)。在游离裂殖子中，检测到了MSP7(22)和仅在一些寄生虫株中存在的进一步切割产物MSP7(19)；这两种衍生物在红细胞入侵期间作为与MSP1片段的蛋白复合物的一部分脱落。MSP7的初级加工对布雷菲德菌素A敏感，而二次加工对钙螯合剂和丝氨酸蛋白酶抑制剂均有抗性。MSP7的初级加工在高尔基体后区室中先于MSP1进行，而二次切割发生在发育中的裂殖子表面，可能在MSP1初级加工时，并且远早于MSP1的二次加工。
