Product Description

Rat C1q is purified from pooled normal rat serum. C1q is part of the C1 complex, which is thefirst complement component in the classical pathway of complement. The C1 complex is a non-covalent assembly ofthree different proteins (C1q, C1r, and C1s) bound together in acalcium-dependent complex. C1q has sixextended arms with domains at the end of each arm that bind to the Fc domainsof immunoglobulins such as IgG or IgM.When antibodies bind to antigens, forming immune complexes, they clusterallowing two or more of the six C1q arms to bind to the Fc domains ofantibodies. Rat IgG2 is very efficientwhen compared to IgG1 in activating complement (Medgyesi, G.A et., al., 1981).This is in contrast to the human system in which IgG1 activates complement butnot IgG2 (Redpath, S. et. al., 1998). Thebinding of multiple arms of C1q to immune complexes causes the two C1r proteinsin the complex (protease zymogens) to auto-activate. The activated C1r proteasescleave and activate the two C1s protease zymogens in the complex. The activated C1s cleaves complementcomponent C4 releasing C4a and initiating covalent attachment of C4b to theactivating surface. Activated C1s alsocleaves C2 and the larger fragment of C2 binds to the surface-attached C4bforming C4b,C2a, the C3/C5 convertase of the classical pathway.

Rat IgG1 cannot activate complement whereas rat IgG2 does.

(For full product description see link...)

Complement Technology的C1是级联反应中的第一个补体成分，称为补体经典途径。C1与抗原结合的抗体（免疫复合物）结合并被其激活，从而产生引发级联反应的蛋白酶。C1实际上是钙依赖性复合物中结合在一起的三种不同蛋白质（C1q，C1r和C1s）的非共价复合物。C1q通过其六个臂中的两个或多个与IgG或IgM的Fc结构域结合。多臂与免疫复合物的结合被认为会引入压力，从而导致复合物中的两个C1r蛋白（蛋白酶酶原）自身激活，从而产生两种活性的C1r丝氨酸蛋白酶（Morikis，D.和Lambris，JD（2005））。 。这些激活的C1r亚基裂解并激活复合物中的两个C1s蛋白酶酶原。活化的C1裂解补体成分C4，释放出C4a，并启动C4b与活化表面的共价连接。活化的C1也切割C2，并且C2的较大片段结合至表面附着的C4b，形成C4b，C2a，其为经典途径的C3 / C5转化酶。