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Comparative Study
. 1996 Aug 6;93(16):8546-51.
doi: 10.1073/pnas.93.16.8546.

Multiple Forms of Complement C3 in Trout That Differ in Binding to Complement Activators

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Comparative Study

Multiple Forms of Complement C3 in Trout That Differ in Binding to Complement Activators

J O Sunyer et al. Proc Natl Acad Sci U S A. .
Free PMC article


In all other species analyzed to date, the functionally active form of complement component C3 exists as the product of a single gene. We have now identified and characterized three functional C3 proteins (C3-1, C3-3, and C3-4) in trout that are the products of at least two distinct C3 genes. All three proteins are composed of an alpha-and a beta-chain and contain a thioester bond in the alpha-chain. However, they differ in their electrophoretic mobility, glycosylation, reactivity with monospecific C3 antibodies, and relative ability to bind to various surfaces (zymosan, Escherichia coli, erythrocytes). A comparison of the partial amino acid sequences of the three proteins showed that the amino acid sequence identity/similarity of C3-3 to C3-4 is 87/91%, while that of C3-3 and C3-4 to C3-1 is 51.5/65.5% and 60/73% respectively. Thus, trout possess multiple forms of functional C3 that represent the products of several distinct genes and differ in their ability to bind covalently to various complement activators.

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