中文摘要：

非晶状体βγ-晶状体蛋白与三叶因子蛋白复合物（[ST-CAT）是从大蹼铃蟾（Bombinamaxima）皮肤分泌物中分离的分子量为72kDa的天然蛋白复合物。本研究通过激光共聚焦显微镜和Westemblot分析βγ-CAT在人脐静脉内皮细胞（HUVEC）中的细胞核转运机制，以及βγ-CAT对多株肿瘤细胞（HCT116，HT29，A375，Hela，THP—1等）的细胞毒效应。结果表明：βγ-CAT的α亚基中含有典型的GTP／ATPase的保守结构模体WalkerA和walkerB，体外检测到βγ-CAT具有GTP／ATP水解酶和GTP／ATP结合活性。在细胞核转运过程中，βγ-CAT的α亚基和B亚基参与形成约150kDa含有泛素化修饰信号的大分子复合物，且泛素化修饰信号和βγ-CAT的α亚基和β亚基共定位于细胞内和融合于细胞核区域的转运囊泡小体中。βγ-CAT能够选择性的杀伤肿瘤细胞，诱导肿瘤细胞脱落和发生凋亡。上述结果为进一步深入研究βγ-CAT的细胞核转运和调节细胞功能的分子作用机制提供思路和线索。

英文摘要：

βγ-CAT is a naturally existing protein complex of non-lens βγ-crystallin and trefoil factor, purified from Bombina maxima skin secretions. In HUVECs, βγ-CAT can be rapidly endocytosed via intracellular vacuole formation and translocated to the nucleus to regulate cell ruction. In this paper, we found that it contains conserved Walker B motifs （IILYDEPS, residues 6-13） and Walker A motifs （GQSLSGKS, residues 96-103） in the βγ-CAT α-subunit sequence. βγ-CAT showed potential NTP-binding and weak GTPase/ATPase activities in vitro. Through Western blotting analysis, we found that the α- and β-subunits of βγ-CAT participated in a 150kDa SDS-stable protein complex formation, which also contained positive ubiquitination signals in the βγ-CAT treated HUVEC. Furthermore, under confocal microscopy, the immunofluorescence signals of ubiquitin and βγ-CAT subunits were co-localized in the vacuoles that were distributed in the cytoplasm and nucleus. In addition, βγ-CAT could induce several tumor cell＇s detachment and apoptosis, and selectively kill tumor cells. These findings provide a clue to understand the mechanism of βγ-CAT endocysis and nuclear transport, and give an insight to investigate the possible occurrence of similar molecule＇s cellular functions and action mechanisms of non-lens βγ-crystallins and trefoil factors in mammals.