Pearce J Andrew, Mills Kerry, Triglia Tony, Cowman Alan F, Anders Robin F
Infection and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, Vic. 3050, Australia.
Mol Biochem Parasitol. 2005 Feb;139(2):141-51. doi: 10.1016/j.molbiopara.2004.09.012.
The merozoite surface of the pathogenic malaria parasite Plasmodium falciparum is comprised of proteins that are important for the identification and invasion of human red cells. Merozoite surface protein (MSP)3 is a polymorphic protein associated with the surface of merozoites and is also a vaccine candidate. A distinct feature of the MSP3 sequence is three blocks of alanine-rich heptad repeats that are predicted to form an intramolecular coiled-coil. Three orthologues of MSP3 that also contain alanine-rich heptad repeats have been described in P. vivax and we therefore searched the P. falciparum genome database for MSP3 paralogues. We have identified two genes, H101 and H103 related to MSP3, however like another MSP3 paralogue, MSP6, H101 and H103 do not contain heptad repeats. H101 and H103 are expressed during the asexual cycle and immunofluorescence indicates H103 localises to the merozoite surface as a peripheral membrane protein. Transfected parasite lines that express truncated forms of H101 or H103 were viable and grew at the same rate as the parental parasite line. This result may reflect redundancy in function among members of the MSP3/MSP6 gene family as has been described for other families of paralogue genes in P. falciparum.
致病性疟原虫恶性疟原虫的裂殖子表面由对人类红细胞的识别和入侵至关重要的蛋白质组成。裂殖子表面蛋白（MSP）3是一种与裂殖子表面相关的多态性蛋白，也是一种疫苗候选物。MSP3序列的一个显著特征是三个富含丙氨酸的七肽重复序列块，预计会形成分子内卷曲螺旋结构。在间日疟原虫中已描述了三个同样含有富含丙氨酸七肽重复序列的MSP3直系同源物，因此我们在恶性疟原虫基因组数据库中搜索MSP3旁系同源物。我们鉴定出了两个与MSP3相关的基因，H101和H103，然而，与另一个MSP3旁系同源物MSP6一样，H101和H103不包含七肽重复序列。H101和H103在无性生殖周期中表达，免疫荧光显示H103作为外周膜蛋白定位于裂殖子表面。表达H101或H103截短形式的转染寄生虫株是有活力的，并且生长速度与亲本寄生虫株相同。这一结果可能反映了MSP3/MSP6基因家族成员之间功能上的冗余，正如对恶性疟原虫中其他旁系同源基因家族所描述的那样。
