Send to

Choose Destination
See comment in PubMed Commons below
Proc Natl Acad Sci U S A. 1994 Mar 29;91(7):2478-82.

Molecular cloning of bullfrog saxiphilin: a unique relative of the transferrin family that binds saxitoxin.

Author information

  • 1Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510.


Plasma and tissue of certain vertebrates contain a protein called saxiphilin that specifically binds the neurotoxin saxitoxin with nanomolar affinity. We describe the isolation of a cDNA clone of saxiphilin from liver of the North American bullfrog (Rana catesbeiana). The cDNA sequence encodes a protein that is evolutionarily related to members of the transferrin family of Fe(3+)-binding proteins. Pairwise sequence alignment of saxiphilin with various transferrins reveals amino acid identity as high as 51% and predicts 14 disulfide bonds that are highly conserved. The larger size of saxiphilin (91 kDa) versus serum transferrin (approximately 78 kDa) is primarily due to a unique insertion of 144 residues. This insertion contains a 49-residue domain classified as a type 1 repetitive element of thyroglobulin, which is shared by a variety of membrane, secreted, and extracellular matrix proteins. Saxiphilin also differs from transferrins in 9 of 10 highly conserved amino acids in the two homologous Fe3+/HCO3-binding sites of transferrin. Identification of saxiphilin implies that transferrin-like proteins comprise a diverse superfamily with functions other than iron binding.

[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Support Center