title: Ancient origin of the complement lectin pathway revealed by molecular cloning of mannan binding protein-associated serine protease from a urochordate, the Japanese ascidian, Halocynthia roretzi.
abstract: Recent identification of a C3-like gene in sea urchins revealed the presence of a complement system in invertebrates. To elucidate further the components and function of the pre-vertebrate complement system, we attempted to isolate an ascidian (urochordata) C3 convertase. After identification of C3 cDNA from Halocynthia roretzi, a Japanese ascidian, reverse transcriptase-PCR amplification of hepatopancreas RNA was performed using primers encoding highly conserved amino acid sequences of the vertebrate Bf and C2 serine protease domain. Two candidate sequences were identified, and the corresponding cDNA clones were isolated from a hepatopancreas library. Surprisingly, neither clone is related to Bf/C2 but rather share the same domain structure of mammalian C1r/C1s/MASP (mannan binding protein-associated serine protease), and are more related evolutionarily to mammalian MASP than to mammalian C1r or C1s. The identification of the tunicate MASP clones, amplified with primers designed to amplify Bf or C2, suggests that the lectin pathway antedated the classical and alternative pathways of complement activation.
authors.affiliation: Department of Biochemistry, Nagoya City University Medical School, Mizuho-ku, Nagoya 467, Japan.
authors.forename: X
authors.initials: X
authors.lastname: Ji
authors.forename: K
authors.initials: K
authors.lastname: Azumi
authors.forename: M
authors.initials: M
authors.lastname: Sasaki
authors.forename: M
authors.initials: M
authors.lastname: Nonaka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D003001:Cloning, Molecular; D037222:Collectins; D003176:Complement C3 / Q000737:chemistry; D050577:Complement C3-C5 Convertases / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D017931:DNA Primers; D018076:DNA, Complementary; D019143:Evolution, Molecular; D008322:Mammals; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000276:immunology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D014158:Transcription, Genetic; D014561:Urochordata / Q000201:enzymology* / Q000235:genetics / Q000276:immunology
chemical_list: D002352:Carrier Proteins; D037222:Collectins; D003176:Complement C3; D017931:DNA Primers; D018076:DNA, Complementary; D011994:Recombinant Proteins; D050577:Complement C3-C5 Convertases; D012697:Serine Endopeptidases