The CaaX proteases are closely related in the post-translational modification of many membrane-bound or secreted proteins and play a key role in the activation or stabilization of these molecules belonging to the CAAX family. In this study, a full-length cDNA putatively encoding a FACE-1/Ste24p CaaX protease (type I) of the Schistosoma japonicum was isolated. The cDNA, named SjSte24p, composed of 1646 bp and encoded 473 amino acids with predicted Mr/pI as 54.77 kDa/8.04. SjSte24p is a monoexonic gene constantly expressed in the parasite from cercariae to adult stages. It contained the characteristic of CaaX protease topology, including seven trans-membrane domains and a metallo-protease segment with a zinc-binding motif (HEXXH). SjSte24p shared a considerable degree of sequence identity with the type I CaaX proteases. A phylogenetic analysis showed that this protein family is tightly conserved from fungi to vertebrates. The expressed recombinant SjSte24p protein showed a proteolytic activity, which was inhibited by EDTA. Its activity was increased at low doses of the Zn²⁺ (0.001-0.01 mM); but was reversibly down-regulated at high doses (>0.1 mM). The native SjSte24p appeared to function in insoluble from. The protein was mainly localized in the tegument on the surface of adult worms. These results indicated that the SjSte24p is a practical zinc-dependent metalloprotease, which belongs to the FACE-1/Ste24p protease family.

CaaX蛋白酶与许多膜结合或分泌的蛋白的翻译后修饰密切相关，并且在这些属于CAAX家族的分子的激活或稳定中起关键作用。在这项研究中，分离出假定编码日本血吸虫的FACE-1 / Ste24p CaaX蛋白酶（I型）的全长cDNA 。该cDNA名为SjSte24p，由1646 bp组成，编码473个氨基酸，预测的Mr / pI为54.77 kDa / 8.04。SjSte24p是从尾c到成虫阶段不断在寄生虫中表达的单外显子基因。它包含CaaX蛋白酶拓扑结构的特征，包括七个跨膜结构域和一个具有锌结合基序（HEXXH）的金属蛋白酶片段。SjSte24p与I型CaaX蛋白酶具有相当程度的序列同一性。系统发育分析表明，该蛋白家族从真菌到脊椎动物都非常保守。表达的重组SjSte24p蛋白表现出蛋白水解活性，该活性被EDTA抑制。在低剂量的Zn ²⁺下其活性增加（0.001-0.01 mM）；但在高剂量（> 0.1 mM）时可逆地下调。天然SjSte24p似乎起不可溶的作用。该蛋白质主要定位在成虫的表面上。这些结果表明，SjSte24p是一种实用的锌依赖性金属蛋白酶，属于FACE-1 / Ste24p蛋白酶家族。