Complete amino acid sequences of the three collagen-like regions present in subcomponent C1q of the first component of human complement.

The sequences of amino acid residues 38--51 of the A-chain, and residues 42--90 of the C-chain, of human subcomponent C1q are given. These results, along with previously published sequence data [Reid (1974) Biochem.J. 141, 189--203; Reid (1977) Biochem.J. 161, 247--251; Reid & Thompson (1978) Biochem.J. 173, 863--868] allow the presentation, and comparison with each other, of the complete amino acid sequences of the collagen-like regions found in the A-, B- and C-chains of human subcomponent C1q. Each chain has the continuity of its collagen-like Gly-X-Y repeating triplet amino acid sequence broken. The B- and C-chains have alanine residues at positions B-9 and C-36 where glycine might be expected. The A-chain has a threonine residue at position A-39, which is located between two Gly-X-Y triplets.