title: Cloning and characterization of cDNAs encoding the complete sequence of decay-accelerating factor of human complement.
abstract: cDNAs encoding the complement decay-accelerating factor (DAF) were isolated from HeLa and differentiated HL-60 lambda gt cDNA libraries by screening with a codon preference oligonucleotide corresponding to DAF NH2-terminal amino acids 3-14. The composite cDNA sequence showed a 347-amino acid protein preceded by an NH2-terminal leader peptide sequence. The translated sequence beginning at the DAF NH2 terminus encodes four contiguous approximately equal to 61-amino acid long repetitive units of internal homology. The repetitive regions contain four conserved cysteines, one proline, one glycine, one glycine/alanine, four leucines/isoleucines/valines, one serine, three tyrosines/phenylalanines, and one tryptophan and show striking homology to similar regions previously identified in factor B, C2, C4 binding protein, factor H, C1r, factor XIII, interleukin 2 receptor, and serum beta 2-glycoprotein I. The consensus repeats are attached to a 70-amino acid long segment rich in serine and threonine (potential O-glycosylation sites), which is in turn followed by a stretch of hydrophobic amino acids. RNA blot analysis of HeLa and HL-60 RNA revealed three DAF mRNA species of 3.1, 2.7, and 2.0 kilobases. The results indicate that portions of the DAF gene may have evolved from a DNA element common to the above proteins, that DAF cDNA predicts a COOH-terminal anchoring polypeptide, and that distinct species of DAF message are elaborated in cells.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018958:CD55 Antigens; D002460:Cell Line; D003001:Cloning, Molecular; D003169:Complement Inactivator Proteins / Q000235:genetics*; D004247:DNA / Q000378:metabolism*; D005796:Genes; D006367:HeLa Cells / Q000276:immunology; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D018958:CD55 Antigens; D003169:Complement Inactivator Proteins; D008565:Membrane Proteins; D004247:DNA