title: Characterization of Xenopus laevis complement factor I structure--conservation of modular structure except for an unusual insert not present in human factor I.
abstract: Factor I (C3b/C4b inactivator) is a regulatory protein of the classical and alternative complement pathways. In this paper, we report the sequence of Xenopus factor I cDNA and the deduced protein structure. The basic structure of human preprofactor I, NH2-heavy chain-cleavage peptide-light chain-COOH, is conserved in the frog. However, the frog heavy chain contains a highly charged segment of 29 amino acids, encoded by a poly dA-rich mRNA insert, which is not found in human factor I. The modular structure of the frog heavy chain was analyzed, and found to differ vis-à-vis previously published analyses of human factor I. We also evaluate the timing of factor I transcription during frog embryogenesis.
authors.affiliation: Department of Hematology/Oncology, Children's Hospital, Boston, MA 02115.
authors.forename: L M
authors.initials: LM
authors.lastname: Kunnath-Muglia
authors.forename: G H
authors.initials: GH
authors.lastname: Chang
authors.forename: R B
authors.initials: RB
authors.lastname: Sim
authors.forename: A J
authors.initials: AJ
authors.lastname: Day
authors.forename: R A
authors.initials: RA
authors.lastname: Ezekowitz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002645:Chickens; D003001:Cloning, Molecular; D017244:Complement Factor I / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification; D004625:Embryo, Nonmammalian / Q000276:immunology; D015723:Gene Library; D007798:Lampreys; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009841:Oligonucleotides; D016133:Polymerase Chain Reaction; D012313:RNA / Q000032:analysis / Q000096:biosynthesis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics / Q000276:immunology*
chemical_list: D009841:Oligonucleotides; D012313:RNA; D004247:DNA; D017244:Complement Factor I