Evidence of homology between the β-chain of human haptoglobin and the chymotrypsin family of serine proteases

✍ Scribed by Alexander Kurosky; Don R. Barnett; Marily A. Rasco; Tong-Ho Lee; Barbara H. Bowman

• Book ID: 104785069
• Publisher: Springer
• Year: 1974
• Tongue: English
• Weight: 705 KB
• Volume: 11
• Category: Article
• ISSN: 0006-2928
• DOI: 10.1007/bf00485995

✦ Synopsis

Amino acid sequences from the fl-chain of human haptoglobin are compared with those sequences known for the serine pro teases of the ehymotrypsin family. In a comparison of some 171 residues of the haptoglobin fl-ehain (approximately 60% of the protein molecule), approximately 30%o of these are identical to residues occurring in sequences of either bovine trypsin, bovine chymotrypsin A, bovine chymotrypsin B, porcine elastase, or bovine thrombin B-chain, and an additional 10% are chemically similar. A combined comparison of the haptoglobin fl-ehain with the above five serine proteases gave an identity of 56% and a chemical similarity of 11%. Similarity of primary structure is also striking around two of the five half-cystinyl residues so far characterized in long lengths of sequence. These data provide substantial evidence that the fl-ehain of haptoglobin is homologous to the ehymotrypsin family of serine proteases. Proposals are also presented to explain the occurrence of internal homology in the Nterminal region of the fl-chain.