Hagfish humoral defense protein exhibits structural and functional homology with mammalian complement components

Peter J. Hanley, Jeffrey W. Hook, David A. Raftos, Andrew A. Gooley, Ronald Trent, Robert L. Raison*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

52 Citations (Scopus)


A genomic clone and cDNA fragment encoding a portion of a humoral recognition molecule from the hagfish were isolated and sequenced. The serum protein has previously been described as having structural features that are immunoglobulin-like. Amino acid sequence obtained from the 77-kDa H1 heavy chain facilitated the isolation of a genomic clone containing at least two coding regions. Through use of primers derived from the genomic sequences, a 231-base-pair cDNA fragment was obtained by PCR from liver RNA. Comparison of the deduced 120-amino acid sequence from the N terminus of H1 with known protein sequences revealed substantial sequence similarity with the β chain of the murine fourth complement component C4 and with the related third and fifth complement molecules C5 and C3 and the major histocompatibility complex-encoded sex-limited protein. Observation of structural and functional similarities associated with the sequence similarity indicate that these molecules share an evolutionary relationship: the polypeptide chain structure of hagfish complement-like protein (CLP) resembles that of C4; CLP contains a hidden thioester group on the 70-kDa chain; CLP binds to streptococcal cells and enhances the phagocytosis of yeast by hagfish leukocytes. These data suggest that CLP forms part of a non-clonally-derived complement-related humoral defense system in the hagfish.

Original languageEnglish
Pages (from-to)7910-7914
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number17
Publication statusPublished - 1 Sep 1992


  • Agnathan
  • Immune response
  • Nucleotide sequence
  • Opsonin


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