Saarela J, Rehn M, Oikarinen A, Autio-Harmainen H, Pihlajaniemi T
Department of Medical Biochemistry, University of Oulu, Finland.
Am J Pathol. 1998 Aug;153(2):611-26. doi: 10.1016/S0002-9440(10)65603-9.
Two N-terminal ends of human type XVIII collagen chains have recently been identified. The two chains have different signal peptides and variant N-terminal noncollagenous NC1 domains of 493 (NC1-493) and 303 (NC1-303) amino acid residues, respectively, but share 301 residues of their NC1 domains as well as the collagenous and C-terminal noncollagenous portions of the molecule. Antibodies were produced against the NC1 region common to both human alpha1(XVIII) chain variants and against NC1 sequences specific to the long variant and were used in combination with in situ hybridization to localize this collagen in a number of human tissues. They were also used for Western blotting, which resulted in detection of overlapping high-molecular weight bands above the 200-kd standard in a kidney extract. Heparin lyase II and heparin lyase III digestions of kidney and placenta extracts indicated that at least in these tissues, type XVIII collagen contains heparin sulfate glycosaminoglycan side chains. Type XVIII collagen was found to be a ubiquitous basement membrane component, occurring prominently at vascular and epithelial basement membranes throughout the body. Comparison of the expression of the NC1-493 and NC1-303 variants revealed marked differences. The short variant was found in most conventional basement membranes, including blood vessels and the various epithelial structures, and around muscular structures. The long variant was expressed very strongly in liver, where it was virtually the only variant in the liver sinusoids, and it occurred only in minor amounts elsewhere. Thus, the 192 N-terminal residues specific to the long variant apparently confer some functional property needed above all in the liver sinusoids, but also at certain other locations.
最近已鉴定出人类 XVIII 型胶原蛋白链的两个 N 末端。这两条链具有不同的信号肽，其 N 末端非胶原 NC1 结构域分别为 493 个氨基酸残基（NC1-493）和 303 个氨基酸残基（NC1-303），但它们的 NC1 结构域有 301 个残基相同，并且分子的胶原部分和 C 末端非胶原部分也相同。制备了针对人类α1(XVIII)链两种变体共有的 NC1 区域以及长变体特有的 NC1 序列的抗体，并将其与原位杂交结合使用，以在多种人体组织中定位这种胶原蛋白。它们还用于蛋白质印迹分析，结果在肾脏提取物中检测到高于 200-kd 标准的重叠高分子量条带。对肾脏和胎盘提取物进行肝素酶 II 和肝素酶 III 消化表明，至少在这些组织中 XVIII 型胶原蛋白含有硫酸乙酰肝素糖胺聚糖侧链。发现 XVIII 型胶原蛋白是一种普遍存在的基底膜成分，在全身的血管和上皮基底膜中显著存在。对 NC1-493 和 NC1-303 变体表达的比较显示出明显差异。短变体存在于大多数传统基底膜中，包括血管、各种上皮结构以及肌肉结构周围。长变体在肝脏中强烈表达，在肝血窦中几乎是唯一的变体，而在其他地方仅少量存在。因此，长变体特有的 192 个 N 末端残基显然赋予了一些功能特性，这些特性首先在肝血窦中是必需的，但在某些其他位置也需要。
