Sorvillo J, Gigli I, Pearlstein E
Biochem J. 1985 Feb 15;226(1):207-15. doi: 10.1042/bj2260207.
The interaction of purified human plasma fibronectin with the C1q subcomponent of complement was investigated by using a solid-phase radiobinding assay. 125I-fibronectin binding to native C1q, purified collagen domain (C1q-c) or globular domain (C1q-g) was compared. When the purified domains were insolubilized by binding to plastic, the C1q-c exhibited 59% of the binding demonstrated with intact C1q, whereas the C1q-g exhibited 35% of the binding. N-Terminal sequencing of the globular domain showed that a sequence of seven collagen-like amino acids was retained on each chain of the C1q-g fragment. 125I-fibronectin binding to C1q could be inhibited equally well by fluid-phase C1q and C1q-c, but not by fluid-phase C1q-g, implying that the collagen-like region retained on the C1q-g is masked in the fluid phase. In addition, studies were performed to determine which subunit(s) of C1q bind(s) fibronectin. The percentages of fibronectin bound by the A, B, and C chain of C1q were found to be 38, 21 and 41% respectively. Inhibition studies with purified 200-180 kDa, 50 kDa or 29 kDa fragments of fibronectin show that the binding site on fibronectin for C1q is the 50 kDa gelatin-binding domain.
采用固相放射结合分析法研究了纯化的人血浆纤连蛋白与补体C1q亚成分之间的相互作用。比较了125I-纤连蛋白与天然C1q、纯化的胶原结构域（C1q-c）或球状结构域（C1q-g）的结合情况。当纯化的结构域通过与塑料结合而不溶时，C1q-c表现出完整C1q所显示结合的59%，而C1q-g表现出35%的结合。球状结构域的N端测序表明，C1q-g片段的每条链上保留了一段由七个胶原样氨基酸组成的序列。液相C1q和C1q-c对125I-纤连蛋白与C1q的结合抑制效果相同，但液相C1q-g则无此作用，这意味着C1q-g上保留的胶原样区域在液相中被掩盖。此外，还进行了研究以确定C1q的哪些亚基与纤连蛋白结合。发现C1q的A、B和C链结合纤连蛋白的百分比分别为38%、21%和41%。用纯化的200-180 kDa、50 kDa或29 kDa纤连蛋白片段进行的抑制研究表明，纤连蛋白上C1q的结合位点是50 kDa的明胶结合结构域。
