Liebau E, Wildenburg G, Walter R D, Henkle-Dührsen K
Department of Biochemistry, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
Infect Immun. 1994 Nov;62(11):4762-7. doi: 10.1128/iai.62.11.4762-4767.1994.
Onchocerca volvulus is a pathogenic human filarial parasite which, like other helminth parasites, is capable of evading the host's immune responses by a variety of defense mechanisms which are likely to include the detoxification and repair mechanisms of the enzyme glutathione S-transferase (GST). In this study, we show that one of the previously described GSTs from O. volvulus appears to possess the characteristics of a secreted enzyme. When the complete O. volvulus GST1 (OvGST1) sequence presented here is compared with those of other GSTs, 50 additional residues at the N terminus are observed, the first 25 showing characteristics of a signal peptide. This is consistent with the N-terminal sequence data on the native mature enzyme which begins at amino acid 26, based on the deduced protein sequence from the cDNA. The native protein, without the signal peptide sequence, possesses a 24-amino-acid extension not present in other GSTs. The deduced amino acid sequence of the OvGST1 cDNA clone was shown to possess four potential N-glycosylation sites. Digestion of O. volvulus homogenate with endoglycosidase, followed by detection of OvGST1 with specific antibody, indicated that the enzyme possesses at least two N-linked oligosaccharide chains. Gel filtration of the Escherichia coli-produced recombinant OvGST1 showed that it is enzymatically active as a nonglycosylated dimer. OvGST1 is found in the media surrounding adult worms maintained in culture, indicating that, in vitro, this enzyme is released from the worm. The strongest immunostaining for OvGST1 was observed in the outer cellular covering of the adult worm body, the syncytial hypodermis, especially in the interchordal hypodermis, where the peripheral membrane forms a series of lamellae which run into the outer zone of the hypodermal cytoplasm.
盘尾丝虫是一种致病性人体丝虫寄生虫，与其他蠕虫寄生虫一样，它能够通过多种防御机制逃避宿主的免疫反应，这些机制可能包括谷胱甘肽S-转移酶（GST）的解毒和修复机制。在本研究中，我们表明，之前描述的来自盘尾丝虫的一种GST似乎具有分泌酶的特征。当将此处呈现的完整盘尾丝虫GST1（OvGST1）序列与其他GST的序列进行比较时，在N端观察到另外50个残基，前25个显示出信号肽的特征。这与基于cDNA推导的蛋白质序列从氨基酸26开始的天然成熟酶的N端序列数据一致。没有信号肽序列的天然蛋白质具有其他GST中不存在的24个氨基酸的延伸。OvGST1 cDNA克隆的推导氨基酸序列显示具有四个潜在的N-糖基化位点。用内切糖苷酶消化盘尾丝虫匀浆，然后用特异性抗体检测OvGST1，表明该酶至少具有两条N-连接的寡糖链。对大肠杆菌产生的重组OvGST1进行凝胶过滤表明，它作为非糖基化二聚体具有酶活性。在培养的成虫周围的培养基中发现了OvGST1，这表明在体外，这种酶是从虫体释放出来的。在成虫体表的外层细胞覆盖物即合胞体皮下组织中观察到对OvGST1的最强免疫染色，特别是在弦间皮下组织中，外周膜形成一系列进入皮下细胞质外层区域的薄片。
