title: Molecular cloning of a lamprey homologue of the mammalian MHC class III gene, complement factor B.
abstract: To elucidate the origin and evolution of the complement system and the MHC, we isolated cDNA clones for the MHC class III complement factor B (Bf) gene from lamprey, one of the most primitive extant vertebrates. A part of the serine protease domain of the lamprey Bf was amplified by reverse transcriptase-PCR using the degenerated primers corresponding to the conserved amino acid stretches between the mouse Bf and C2 sequences. A full-length lamprey Bf cDNA clone was isolated from the lamprey liver cDNA library using a PCR-amplified DNA clone as a probe. The deduced amino acid sequence of 763 residues showed essentially the same domain structure as mammalian Bf or C2, consisting of three short consensus repeat domains, a von Willebrand domain, and a serine protease domain. Lamprey Bf showed 33 and 29% overall amino acid similarity to mouse Bf and mouse C2, respectively, whereas amino acid similarity between mouse Bf and mouse C2 was 36%, suggesting that the gene duplication of Bf/C2 occurred in the main line of vertebrate evolution after the divergence of cyclostomes. This is the first report of the molecular cloning from cyclostomes of a component of the mammalian MHC that offers the possibility of genetic analysis of the presumably primitive MHC of cyclostomes.
authors.affiliation: Department of Biochemistry, Nagoya City University Medical School, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nonaka
authors.forename: M
authors.initials: M
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Sasaki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D011415:Complement Factor B / Q000235:genetics*; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D007798:Lampreys / Q000235:genetics* / Q000276:immunology*; D008322:Mammals; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000235:genetics; D013045:Species Specificity
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D012313:RNA; D012697:Serine Endopeptidases; D011415:Complement Factor B