PMID: 6976993Mar 1, 1982Paper

The fourth component of human complement treated with amines or chaotropes or frozen-thawed (C4b-like C4): interaction with C4 binding protein and cleavage by C3b/C4b inactivator

The Journal of Immunology : Official Journal of the American Association of Immunologists
I von ZabernI Gigli

Abstract

We have shown previously that C4 treated with amines or chaotropes, although uncleaved, exhibits properties that are similar to C4b. Studies by other groups suggest that this C4b-like form of C4 is characterized by the lack of an internal thiolester bond that is present in native C4. We report here that C4 treated with N2H4 or KSCN or frozen-thawed, unlike native C4, forms a complex with C4-binding protein (C4-bp) and is cleaved by C3b/C4b inactivator (I). Fragmentation of C4b-like C4 by I occurs without previous cleavage to C4b and requires the presence of C4-bp. Cleavage of C4b-like C4 proceeds in two steps: a small fragment (16,000 m.w.) is released first, followed by cleavage of the remaining alpha-chain fragment (83,000 m.w.) into polypeptides of 46,000 (C4d) and 32,000 m.w. All fragments, except the 46,000 m.w. fragment, are disulfide-linked to the beta- and/or gamma-chains of C4. Cleavage of C4b-like C4 probably occurs at the same points in the alp a-chain as in C4b; however, C4b-like c4 also contains C4a. Based on the m.w. determinations, the C4a portion of the alpha-chain is present in the 83,000 m.w. fragment, and after the second cleavage, in the 32,000 m.w. fragment of C4b-like C4. These findings suggest the followi...Continue Reading

Citations

Jan 1, 1983·Springer Seminars in Immunopathology·B F Tack
Jun 17, 2009·Infection and Immunity·Karita HaapasaloT Sakari Jokiranta
Jan 1, 1983·International Journal of Immunopharmacology·I von ZabernW Sachsenheimer
Jan 30, 2014·Journal of Immunological Methods·Katrine PilelyYaseelan Palarasah

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