抄録
Since the cleavage products of C4 are guides to classical pathway activation, we have extended our previous studies in order to characterize the mobility on immunoelectrophoresis, chain structure and amino termini of the products produced by Cls and the further degradation by the C3b-C4b inactivator combined with a high molecular weight (10S) heat and DFP resistant factor. C4 has three chain structure and the NH2-terminus of the α and γ chains was Glx, while that of the β chain was not detected. On addition of purified Cls, the NH2-terminal portion of the α chain of C4 was released and C4a and C4b could be identified. Ala was the newly liberated NH2-terminus of C4b. Highly purified C4b was then reacted both sequentially or collectively with the C4b INA and the additional 10S cofactor. Alteration of the structure of C4b was detectable only if the purified proteins were present simultaneously. Cleavage into two components, C4c with a molecular weight of 14×104 and C4b, the α mobility fragment (molecular weight 5.8×104) was found.
