Product Description

Rat C3 is purifiedfrom pooled normal rat serum. C3 is central to the activation of allthreepathways of complement activation (Law, S.K.A. and Reid, K.B.M.(1995)).Initiation of each pathway generates proteolytic enzymecomplexes (C3convertases) which are bound to the target surface. Theseenzymes cleave apeptide bond in C3 releasing the anaphylatoxin C3aand activating C3b. For abrief time (~60 µs) this nascent C3b iscapable of reacting with and covalentlycoupling to hydroxyl groups onthe target surface. Carbohydrates are thefavored target, but proteinhydroxyls and amino groups also react. This processof tagging thetarget surface with C3b is called opsonization. The reactivesite innascent C3b is a thioester (Tack B.J., et al. (1980); Pangburn M.K. and MüllerEberhard H.J. (1980)) and C3b is linked to the target through acovalentester bond (an amide bond is formed if C3b is attached toamino groups). Mostof the C3 activated during complement activationnever attaches to the surfacebecause its thioester reacts with waterforming fluid phase C3b which israpidly inactivated by factors H and Iforming iC3b. Surface-bound C3b isnecessary in all three pathways forefficient activation of C5 and formation ofC5b-9 complexes that lysethe target cell membrane. Surface-bound C3b and itsbreakdown productsiC3b and C3d are recognized by numerous receptors onlymphoid andphagocytic cells which use the C3b ligand to stimulate antigen presentation to cells of the adaptive immune system. The end result isanexpansion of target-specific B-cell and T-cell populations.

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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。