A COMPLEMENT FACTOR B-LIKE CDNA CLONE FROM THE ZEBRAFISH (BRACHYDANIO-RERIO)

An important molecule in the activation of the complement system in ve rtebrates is factor B, a serine protease with a molecular mass of 95,0 00. Factor B and the complement component C2 are thought to have arise n by gene duplication. In mammals and in Xenopus the factor B gene is linked to the major histocompatibility complex (MHC), whereas in domes tic fowl it segregates independently of the MHC. Here we describe the isolation of a cDNA clone coding for factor B in the zebrafish, Brachy danio rerio. The deduced protein sequence exhibits a characteristic mo saic structure consisting of the short consensus repeat (SCR), the von Willebrand factor, and the serine protease domains. The estimated tim e of factor B and C2 divergence (approximately 350 million years ago), combined with the fact that C2 has thus far been found only in mammal s, suggest that the factor B-C2 gene duplication occurred after the di vergence of mammal-like reptiles from other reptiles and hence also bi rds. After the duplication, the C2 component evolved significantly fas ter than factor B. Copyright (C) 1996 Elsevier Science Ltd.