Douglas S P, Jenkins J M, Kadler K E
Wellcome Trust Center for Cell-Matrix Research, School of Biological Sciences, University of Manchester, UK.
Matrix Biol. 1998 Mar;16(8):497-505. doi: 10.1016/s0945-053x(98)90020-8.
Collagen IX, a structural component of the extracellular matrix of connective tissues, is synthesized as long and short forms which contain or lack, respectively, a 27 kDa non-collagenous (NC) 4 domain at the N-terminus of the alpha 1(IX) chain of the molecule. The long form occurs in cartilage and developing cornea, but not in vitreous, suggesting a specialized function for the NC4 domain, perhaps by interacting with other macromolecules. To test this hypothesis, embryonic chick cartilage was treated with DTSSP, dissociated with bacterial collagenase, and the NC4-containing DTSSP-cross-linked protein complexes examined and purified. Analysis of cartilage extracts using an anti-NC4 antibody, and of purified NC4-containing complexes, identified a predominant NC4 dimer. A naturally-occurring N-terminal fragment of the alpha 1(IX) chain, whose size is equivalent to the NC4-COL3-NC3 domains of the chain, was identified. Association of collagen IX molecules via NC4 domains and the existence of a cleavage site close to the NC3 domain of the molecule are likely to be of primary importance in the growth and remodeling processes of cartilage, in health and disease.
IX型胶原蛋白是结缔组织细胞外基质的一种结构成分，它以长形式和短形式合成，长形式和短形式分别在该分子α1(IX)链的N端含有或缺少一个27 kDa的非胶原（NC）4结构域。长形式存在于软骨和发育中的角膜中，但不存在于玻璃体中，这表明NC4结构域具有特殊功能，可能是通过与其他大分子相互作用来实现的。为了验证这一假设，用二硫代琥珀酰亚胺基丙酸（DTSSP）处理胚胎鸡软骨，用细菌胶原酶使其解离，然后对含有NC4的DTSSP交联蛋白复合物进行检查和纯化。用抗NC4抗体分析软骨提取物以及纯化的含NC4复合物，鉴定出一种主要的NC4二聚体。鉴定出了α1(IX)链的一个天然存在的N端片段，其大小与该链的NC4-COL3-NC3结构域相当。IX型胶原蛋白分子通过NC4结构域的缔合以及分子中靠近NC3结构域处存在一个切割位点，可能在软骨生长和重塑过程（无论健康还是患病状态下）中起着至关重要的作用。
