title: Molecular cloning of human C1 inhibitor: sequence homologies with alpha 1-antitrypsin and other members of the serpins superfamily.
abstract: Genetic and acquired diseases in man show that the proteolytic activity of the complement component C1 is crucially regulated by C1 inhibitor (C1-INH), a plasma protein whose suspected relatedness to other serine proteinase inhibitors (serpins) contrasts with its atypically large size and high degree of glycosylation. Indeed we have found that the C1-INH polypeptide precursor synthesized in a cell-free system is a 64-kDa protein, hence it exceeds the length of the precursor forms of typical serpins. Seeking more conclusive sequence information and a probe for the structural locus, we isolated C1-INH cDNA clones from a library representing size-enriched human liver mRNA. Nucleotide sequence analysis of a clone covering the carboxyterminal half of C1-INH conclusively documents the relatedness of this protein with the serpins, and reveals 27% amino acid identity with alpha 1-antitrypsin.
mesh_terms: D003001:Cloning, Molecular; D003174:Complement C1 Inactivator Proteins / Q000235:genetics*; D004247:DNA / Q000235:genetics; D006801:Humans; D008099:Liver / Q000502:physiology; D011480:Protease Inhibitors / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D012694:Serine; D000515:alpha 1-Antitrypsin / Q000235:genetics
chemical_list: D003174:Complement C1 Inactivator Proteins; D011480:Protease Inhibitors; D000515:alpha 1-Antitrypsin; D012694:Serine; D004247:DNA