title: cDNA cloning, sequencing and chromosomal assignment of the gene for mouse complement factor I (C3b/C4b inactivator): identification of a species specific divergent segment in factor I.
abstract: Factor I is an essential regulatory serine proteinase of the complement cascade. It cleaves and inactivates the C3b and C4b constituents of the C3 and C5 convertases and thereby regulates many complement-mediated activities. The human protein is a heterodimer composed of a 50 kDa non-catalytic subunit (which contains several domains, i.e. FIM, CD5, LDLr type A) disulfide linked to a 38 kDa catalytic subunit. Recent characterization of Xenopus factor I cDNA revealed a 29 residue negatively charged region in its heavy chain which is absent in the human protein (Kunnath-Muglia et al., Molec. Immun. 30, 1249-1256, 1993). We report the complete cDNA sequence of mouse factor I as well as a partial chicken factor I cDNA sequence. Alignment of these two sequences with the published sequences for human and Xenopus proteins (a) demonstrates an overall conservation of primary structure and domain organization of mouse factor I, and (b) defines a divergent segment (D segment) in each species. In Xenopus protein, the D segment includes the 29 residue negatively charged region. In each of the four species examined, the D segment differed in length, sequence, organization, and number of repeated subregions. These differences reflect a considerable evolution of D segment. The significance of the diversity of the D segment is at present unclear. We also report the chromosomal localization of the mouse factor I gene (Cfi) to distal chromosome 3 near Egf.
authors.affiliation: Department of Cellular and Molecular Pathology, University of Toronto, Canada.
authors.forename: J O
authors.initials: JO
authors.lastname: Minta
authors.forename: M J
authors.initials: MJ
authors.lastname: Wong
authors.forename: C A
authors.initials: CA
authors.lastname: Kozak
authors.forename: L M
authors.initials: LM
authors.lastname: Kunnath-Muglia
authors.forename: G
authors.initials: G
authors.lastname: Goldberger
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003180:Complement C3b Inactivator Proteins / Q000235:genetics*; D017244:Complement Factor I / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D014982:Xenopus laevis
chemical_list: D003180:Complement C3b Inactivator Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D017244:Complement Factor I