经典抗体介导的补体激活
中文名称
通路描述
C1 是补体系统的第一个组分，是一个包含三种蛋白质物种的复合物，即 C1q、C1r 和 C1s。C1q 由六个相同的亚基组成，每个亚基包含三个同源链（A、B 和 C）。这些链在 C 末端形成球状结构，随后是“颈部”和“茎部”中的线圈。六个亚基由胶原样茎部连接在一起（导致 C1q 与“六朵郁金香”的类比）。茎部也与 [C1s:C1r:C1r:C1s] 四聚体线性链相互作用。抗原与 IgM 或 IgG 类抗体的抗体结合诱导抗体 Fc 区的构象变化，使其能够结合 C1q 组分。C1 激活需要与两个独立的 Fc 域相互作用，因此五价 IgM 抗体比 IgG 抗体更有效地激活补体。抗体结合导致 C1 复合物中 C1r 的构象变化，并引起 C1r 的蛋白酶解，激活它。活性 C1r 则裂解并激活 C1 复合物中的 C1s 组分（Muller-Eberhard 1988）。
英文描述
Classical antibody-mediated complement activation C1, the first component of complement is a complex containing three protein species, C1q, C1r, and C1s. C1q is assembled from six identical subunits each of which consists of three homologous chains (A, B, and C). These chains form a globular domain at the C-terminus, followed by the "neck" and a coil in the "stalk." The six subunits are held together by the collagenous stalk parts (giving rise to the comparison of C1q with a "bunch of six tulips"). The stalks also interact with the [C1s:C1r:C1r:C1s] tetramer assembled in a linear chain. Binding of an antigen to an antibody of the IgM or IgG class induces a conformational change in the Fc domain of the antibody that allows it to bind to the C1q component of C1. C1 activation requires interaction with two separate Fc domains, so pentavalent IgM antibody is far more efficient at complement activation than IgG antibody. Antibody binding results in a conformational change in the C1r component of the C1 complex and a proteolytic cleavage of C1r, activating it. Active C1r then cleaves and activates the C1s component of the C1 complex (Muller-Eberhard 1988).
所含基因
19 个基因