Haemoglobin binding with haptoglobin. Localization of the haptoglobin-binding sites on the beta-chain of human haemoglobin by synthetic overlapping peptides encompassing the entire chain.
A synthetic approach was employed to identify the haptoglobin-binding sites on the beta-chain of human haemoglobin. This approach consists of the synthesis of a series of consecutive overlapping peptides that, together, systematically represent the entire protein chain. Fourteen synthetic peptides (beta 1-15, beta 11-25 etc.) were examined for their ability to bind human haptoglobin by quantitative solid-phase radiometric titrations of 125I-labelled haptoglobin. Of these 14 peptides only peptides beta 11-25 and beta 131-146 bound haptoglobin significantly; peptide beta 21-35 exhibited a small binding activity as a consequence of the overlap with peptide beta 11-25. On this basis and by examination of the three-dimensional structure of haemoglobin, it was concluded that the beta-chain of haemoglobin has two binding sites for haptoglobin that reside in, but do not necessarily encompass all of, the regions beta 11-25 and beta 131-146.
D001665:Binding Sites; D006242:Haptoglobins / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D010455:Peptides / Q000138:chemical synthesis
D006242:Haptoglobins; D006454:Hemoglobins; D010455:Peptides; C035492:haptoglobin-hemoglobin complex