Nakae H, Sugano M, Ishimori Y, Endo T, Obinata T
Advanced Research Laboratory, Research and Development Center, Toshiba Corporation, Japan.
Eur J Biochem. 1993 Apr 1;213(1):11-9. doi: 10.1111/j.1432-1033.1993.tb17729.x.
Entactin/nidogen, a major component of the basement membrane, has a domain structure comprising three globular domains, and thread-like and rod-like domains connecting them. It contains six epidermal-growth-factor-(EGF)-like motifs and one thyroglobulin-like motif. In the present study, ascidian entactin/nidogen has been identified by a monoclonal antibody technique. We prepared anti-(ascidian entactin/nidogen)IgG, named anti-AsEnt1, then cloned the cDNA of ascidian entactin/nidogen using anti-AsEnt1 as a probe, and determined its entire sequence. Mainly because the deduced amino acid sequence exhibited high similarity to mouse entactin and human nidogen, and because the antigen localized in basement membrane of ascidian body-wall muscle, we have concluded that the antigen anti-AsEnt1 corresponds to the ascidian entactin/nidogen homologue. The deduced amino acid sequence of ascidian entactin/nidogen clearly showed that the ascidian homologue also has a domain structure. However, the ascidian homologue lacked the thread-like domain, and the rod-like domain differed from that of mouse entactin in composition, consisting of two kinds of cysteine-rich motifs, that is, the EGF-like motif and the thyroglobulin-like motif. These results suggest that entactin/nidogen have evolved by modifying the domains, especially by shuffling the two kinds of cysteine-rich motifs.
巢蛋白/巢素是基底膜的主要成分，具有包含三个球状结构域以及连接它们的丝状和杆状结构域的结构域结构。它含有六个表皮生长因子（EGF）样基序和一个甲状腺球蛋白样基序。在本研究中，通过单克隆抗体技术鉴定了海鞘巢蛋白/巢素。我们制备了抗（海鞘巢蛋白/巢素）IgG，命名为抗AsEnt1，然后以抗AsEnt1为探针克隆了海鞘巢蛋白/巢素的cDNA，并确定了其完整序列。主要是因为推导的氨基酸序列与小鼠巢蛋白和人巢素具有高度相似性，并且因为抗原定位于海鞘体壁肌肉的基底膜中，我们得出结论，抗AsEnt1抗原对应于海鞘巢蛋白/巢素同源物。海鞘巢蛋白/巢素推导的氨基酸序列清楚地表明，海鞘同源物也具有结构域结构。然而，海鞘同源物缺乏丝状结构域，并且杆状结构域在组成上与小鼠巢蛋白不同，由两种富含半胱氨酸的基序组成，即EGF样基序和甲状腺球蛋白样基序。这些结果表明，巢蛋白/巢素通过修饰结构域，特别是通过改组两种富含半胱氨酸的基序而进化。
