Tomkinson B, Zetterqvist O
Department of Medical and Physiological Chemistry, University of Uppsala, Sweden.
Biochem J. 1990 Apr 1;267(1):149-54. doi: 10.1042/bj2670149.
Tripeptidyl peptidase II (TPP II) is a large intracellular exopeptidase with an active site of the subtilisin type. Affinity-purified hen antibodies against human erythrocyte TPP II cross-reacted with fibronectin in an immunoblot analysis. Furthermore, antibodies against human fibronectin cross-reacted with TPP II. Antibodies against a 65 kDa cell-binding fragment of fibronectin specifically reacted with TPP II, whereas antibodies against the collagen-binding domain, the main heparin-binding domain or the N-terminal fibrin-binding domain did not react. Moreover, the affinity-purified antibodies against TPP II reacted with a 105 kDa cell-binding fragment of fibronectin but not with the fibrin-binding domain or the collagen-binding domain. When native TPP II was dissociated into smaller units through dialysis against a dilute Tris buffer, it could be digested by chymotrypsin into three stable fragments of 70 kDa, 42 kDa and 20 kDa. It could be demonstrated that the 42 kDa fragment was specifically recognized by antibodies against the 65 kDa cell-binding fragment of fibronectin. Furthermore, labelling with di-[3H]isopropyl phosphorofluoridate and N-terminal sequence determination showed that the 70 kDa fragment contained the active-site serine residue. In conclusion, our findings suggest that one domain of the TPP II molecule bears structural resemblance to a cell-binding fragment of fibronectin.
三肽基肽酶II（TPP II）是一种大型细胞内肽链外切酶，具有枯草杆菌蛋白酶类型的活性位点。在免疫印迹分析中，亲和纯化的抗人红细胞TPP II的鸡抗体与纤连蛋白发生交叉反应。此外，抗人纤连蛋白的抗体与TPP II发生交叉反应。抗纤连蛋白65 kDa细胞结合片段的抗体与TPP II特异性反应，而抗胶原结合结构域、主要肝素结合结构域或N端纤维蛋白结合结构域的抗体则不发生反应。此外，亲和纯化的抗TPP II抗体与纤连蛋白的105 kDa细胞结合片段反应，但不与纤维蛋白结合结构域或胶原结合结构域反应。当天然TPP II通过对稀Tris缓冲液进行透析解离成较小的单元时，它可被胰凝乳蛋白酶消化成70 kDa、42 kDa和20 kDa的三个稳定片段。可以证明，42 kDa片段被抗纤连蛋白65 kDa细胞结合片段的抗体特异性识别。此外，用二-[3H]异丙基磷酰氟标记和N端序列测定表明，70 kDa片段含有活性位点丝氨酸残基。总之，我们的研究结果表明，TPP II分子的一个结构域与纤连蛋白的细胞结合片段具有结构相似性。
