title: Characterization and organization of the genes encoding the A-, B- and C-chains of human complement subcomponent C1q. The complete derived amino acid sequence of human C1q.
abstract: A partial cDNA clone for the A-chain of human complement subcomponent C1q was isolated from a monocyte library. Use of the A-chain cDNA clone, and a previously characterized B-chain cDNA clone [Reid (1985) Biochem. J. 231, 729-735] allowed the isolation of overlapping cosmid clones that were shown to contain the genes encoding the A-, B- and C-chains of human C1q. The three genes were found to be aligned, 5'----3', in the same orientation, in the order A-C-B on a 24 kb stretch of DNA on chromosome 1p. The A-, B- and C-chain genes are approx. 2.5, 2.6 and 3.2 kb long respectively, and each contains one intron, located within a codon for a glycine residue found half-way along the collagen-like region present in each chain. These glycine residues are located just before the point where the triple-helical portions of the C1q molecule appear to bend when viewed in the electron microscope. Southern-blot analyses indicated that there is only one gene per chain, and preliminary examination of genomic DNA from several C1q-deficient patients showed no evidence for major deletions or insertions within the A-, B- or C-chain genes. The DNA sequence of the coding region of the C-chain gene allows the completion of the entire derived amino acid sequence for the human C1q molecule. The globular, C-terminal, regions of the chains of C1q show a strong similarity in amino acid sequence to the non-collagen-like, C-terminal, regions of the type VIII and type X collagens, indicating structural and evolutionary relationships between these three molecules.
authors.affiliation: Department of Biochemistry, University of Oxford, U.K.
authors.forename: G C
authors.initials: GC
authors.lastname: Sellar
authors.forename: D J
authors.initials: DJ
authors.lastname: Blake
authors.forename: K B
authors.initials: KB
authors.lastname: Reid
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D003094:Collagen / Q000235:genetics; D015922:Complement C1q / Q000172:deficiency / Q000235:genetics*; D003360:Cosmids; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D015723:Gene Library; D005796:Genes; D006801:Humans; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D009000:Monocytes / Q000378:metabolism; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid
chemical_list: D046911:Macromolecular Substances; D012313:RNA; D015922:Complement C1q; D003094:Collagen; D004247:DNA