Snellman A, Tu H, Väisänen T, Kvist A P, Huhtala P, Pihlajaniemi T
Collagen Research Unit, Biocenter and Department of Medical Biochemistry, University of Oulu, FIN-90220 Oulu, Finland.
EMBO J. 2000 Oct 2;19(19):5051-9. doi: 10.1093/emboj/19.19.5051.
The recombinant transmembrane protein type XIII collagen is shown to reside on the plasma membrane of insect cells in a 'type II' orientation. Expressions of deletion constructs showed that sequences important for the association of three alpha1(XIII) chains reside in their N- rather than C-terminal portion. In particular, a deletion of residues 63-83 immediately adjacent to the transmembrane domain abolished the formation of disulfide-bonded trimers. The results imply that nucleation of the type XIII collagen triple helix occurs at the N-terminal region and that triple helix formation proceeds from the N- to the C-terminus, in opposite orientation to that of the fibrillar collagens. Interestingly, a sequence homologous to the deleted residues was found at the same plasma membrane-adjacent location in other collagenous transmembrane proteins, suggesting that it may be a conserved association domain. The type XIII collagen was secreted into insect cell medium in low amounts, but this secretion was markedly enhanced when the cytosolic portion was lacking. The cleavage occurred in the non-collagenous NC1 domain after four arginines and was inhibited by a furin protease inhibitor.
重组跨膜蛋白 XIII 型胶原蛋白显示以“II 型”方向位于昆虫细胞的质膜上。缺失构建体的表达表明，三条α1(XIII)链缔合的重要序列位于其 N 端而非 C 端部分。特别是，紧邻跨膜结构域的 63 - 83 位残基的缺失消除了二硫键连接三聚体的形成。结果表明，XIII 型胶原蛋白三螺旋的成核发生在 N 端区域，并且三螺旋形成从 N 端向 C 端进行，这与纤维状胶原蛋白的方向相反。有趣的是，在其他胶原跨膜蛋白的相同质膜相邻位置发现了与缺失残基同源的序列，表明它可能是一个保守的缔合结构域。XIII 型胶原蛋白少量分泌到昆虫细胞培养基中，但当胞质部分缺失时，这种分泌明显增强。切割发生在非胶原蛋白 NC1 结构域中四个精氨酸之后，并被弗林蛋白酶抑制剂抑制。
