Furthmayr H, Wiedemann H, Timpl R, Odermatt E, Engel J
Biochem J. 1983 May 1;211(2):303-11. doi: 10.1042/bj2110303.
Intima collagen was studied by electron microscopy (rotary shadowing and negative staining) and by analytical ultracentrifugation. It was found that the monomeric unit (Mr 170 000) consists of a 105 nm-long triple helix terminated by a small globular domain (Mr about 30 000) at one end and a large globular domain (Mr about 40 000) at the other end. The monomer was produced by selective reduction of interchain disulphide bridges. Before reduction, dimers, tetramers and larger filamentous structures were found. Dimers are lateral staggered aggregates of two monomers aligned in an anti-parallel fashion. This gives rise to an inner 75 nm-long region of two slightly intertwisted triple helices flanked by the large globular domains. The outer triple-helical segments (length 30 nm) with the small globular domains at their ends emerge at both sides of this structure. Interchain disulphide bridges are probably located in the vicinity of the large domains. Only the outer segments could be degraded by bacterial collagenase. In tetramers the outer segments of two dimers are covalently linked, forming a scissors-like structure. In the fibrous forms several tetramers are assembled end-to-end with an overlap between the outer segments. The molecular masses and sedimentation coefficients were calculated for these various forms from the electron-microscopically observed dimensions and agreed with results obtained by ultracentrifugation. The unique structure of intima collagen suggests that it originates from a microfibrillar component and that it can be considered a unique collagenous protein, for which we propose the designation type VI collagen.
采用电子显微镜（旋转投影和负染法）及分析超速离心法对内膜胶原蛋白进行了研究。结果发现，单体单元（分子量170000）由一条105纳米长的三螺旋结构组成，一端为一个小的球状结构域（分子量约30000），另一端为一个大的球状结构域（分子量约40000）。单体是通过选择性还原链间二硫键产生的。还原前，发现了二聚体、四聚体及更大的丝状结构。二聚体是由两个以反平行方式排列的单体形成的侧向交错聚集体。这导致了一个内部由两个略微缠绕的三螺旋结构组成的75纳米长的区域，两侧为大的球状结构域。末端带有小球状结构域的外部三螺旋片段（长度30纳米）从该结构的两侧伸出。链间二硫键可能位于大结构域附近。只有外部片段可被细菌胶原酶降解。在四聚体中，两个二聚体的外部片段共价连接，形成类似剪刀的结构。在纤维形式中，几个四聚体首尾相连组装，外部片段之间有重叠。根据电子显微镜观察到的尺寸计算了这些不同形式的分子量和沉降系数，结果与超速离心法得到的结果一致。内膜胶原蛋白的独特结构表明它起源于微原纤维成分，可被视为一种独特的胶原蛋白，我们建议将其命名为VI型胶原蛋白。
