title: A complement factor B-like cDNA clone from the zebrafish (Brachydanio rerio).
abstract: An important molecule in the activation of the complement system in vertebrates is factor B, a serine protease with a molecular mass of 95,000. Factor B and the complement component C2 are thought to have arisen by gene duplication. In mammals and in Xenopus the factor B gene is linked to the major histocompatibility complex (MHC), whereas in domestic fowl it segregates independently of the MHC. Here we describe the isolation of a cDNA clone coding for factor B in the zebrafish, Brachydanio rerio. The deduced protein sequence exhibits a characteristic mosaic structure consisting of the short consensus repeat (SCR), the von Willebrand factor, and the serine protease domains. The estimated time of factor B and C2 divergence (approximately 350 million years ago), combined with the fact that C2 has thus far been found only in mammals, suggest that the factor B-C2 gene duplication occurred after the divergence of mammal-like reptiles from other reptiles and hence also birds. After the duplication, the C2 component evolved significantly faster than factor B.
authors.affiliation: Max-Planck-Institute fur Biologie, Abteilung Immungenetik, Tubingen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Seeger
authors.forename: W E
authors.initials: WE
authors.lastname: Mayer
authors.forename: J
authors.initials: J
authors.lastname: Klein
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003175:Complement C2 / Q000235:genetics; D011415:Complement Factor B / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D015723:Gene Library; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish / Q000235:genetics*
chemical_list: D003175:Complement C2; D017931:DNA Primers; D018076:DNA, Complementary; D011415:Complement Factor B