Mouse C3b/C4b inactivator: purification and properties.

S Kai; T Fujita; I Gigli; V Nussenzweig

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PubMed · 6776193

Mouse C3b/C4b inactivator: purification and properties.

S Kai·T Fujita·I Gigli·V Nussenzweig

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Abstract

Mouse C3b/C4b inactivator (C3b/C4bINA) was purified approximately 400 times from mouse serum. It is a beta-globulin and consists of 2 disulfide bonded chains of m.w. 60,000 and 35,000. Under nonreducing conditions, its m.w. is 95,000. It cleaves the alpha'-chain of cell-bound C4b into 3 fragments: alpha 2, alpha 3, alpha 4. The alpha 2 fragments remain bound to the cell surface (C4d), and the rest of the molecule (C4c) is released into the fluid phase. In fluid phase, C3b/C4bINA cleaves the alpha'-chain of C4b in a similar manner but only in the presence of mouse or human C4-binding protein (C4-bp). Mouse C4-bp and human C3b/C4bINA do not cleave human C4b, although mouse C4-bp binds to human C4b. This incompatibility suggests that C4-bp and C3b/C4bINA must interact to cleave fluid phase C4b. Mouse C3b/C4bINA also cleaves the alpha'-chain of human C3b in solution into 2 fragments in the presence of human beta 1H. Therefore, it is likely that mouse and human C3b/C4bINA are homologous proteins. A monospecific antiserum to mouse C3b/C4bINA has been prepared in rabbits. By crossed immunoelectrophoresis, this antiserum detects, in addition to the protein described above, a fast beta-globulin with a m.w. of approximately 200,000 and antigenically identical to C3b/C4bINA but enzymatically inactive. This protein could represent a precursor of C3b/C4bINA.

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Animals Chemical Phenomena Chemistry Complement C3b Inactivator Proteins Complement C4 Cross Reactions Guinea Pigs Humans Immunodiffusion Immunoelectrophoresis, Two-Dimensional Male Mice Mice, Inbred AKR Molecular Weight Rabbits Journal Article Research Support, U.S. Gov't, P.H.S.

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S Kai, T Fujita, I Gigli, V Nussenzweig. 1980. Mouse C3b/C4b inactivator: purification and properties.. https://pubmed.ncbi.nlm.nih.gov/6776193/

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