title: Completion of the amino acid sequences of the A and B chains of subcomponent C1q of the first component of human complement.
abstract: The sequences of amino acid residues 109--224 of the A chain, and residues 109--22 of the B chain, of human subcomponent C1q are given. These results, along with previously published sequence data on the N-terminal, collagen-like, regions of the A and B chains [Reid (1979) Biochem. J. 179, 367--371] yield the complete amino acid sequences of the A and B chains of subcomponent C1q. The asparagine residue at position A-124 has been identified as the major site of asparagine-linked carbohydrate in subcomponent C1q. When the sequences of the C-terminal, 135-residue-long, 'globular' regions of A and B chains are compared they show 40% homology. The degree of homology over certain stretches of 15--20 residues, within the C-terminal regions, rises up to values of 73%, indicating the presence of strongly conserved structures. Structure prediction studies indicate that both the A and B chain C-terminal regions may adopt a predominantly beta-type structure with apparently little alpha-helical structure.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001216:Asparagine / Q000032:analysis; D002241:Carbohydrates / Q000032:analysis; D003166:Complement Activating Enzymes; D015922:Complement C1q; D006801:Humans; D010446:Peptide Fragments / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D010446:Peptide Fragments; D001216:Asparagine; D015922:Complement C1q; D003166:Complement Activating Enzymes