Accession Number : ADA321585

Title :   Cloning and Functional Analysis of Saxiphilin, A Saxitoxin-Binding Protein from the Bullfrog.

Descriptive Note : Final rept. 1 Mar 93-31 Aug 96,

Corporate Author : YALE UNIV NEW HAVEN CT SCHOOL OF MEDICINE

Personal Author(s) : Moczydlowski, Edward G.

PDF Url : ADA321585

Report Date : OCT 1996

Pagination or Media Count : 98

Abstract : Saxitoxin (STX), a potent neurotoxin, is the causative agent of paralytic shellfish poisoning in humans. The North American bullfrog, Rana catesbeiana, contains a plasma protein called saxiphilin that binds STX with high affinity and specificity. Since saxiphilin may be useful as a detection reagent or an antidote for STX, we have investigated the biochemical properties of saxiphilin and cloned cDNA encoding this protein. Native saxiphilin is a polypeptide of 825 amino acid residues (Mr = 90,901) that contains one binding site for (3H)STX per molecule with an equilibrium dissociation constant of KD = 0.2 nM. The amino acid sequence of saxiphilin, deduced from cDNA isolated from bullfrog liver, exhibits substantial homology to members of the transferrin family of Fe+-binding proteins. However, biochemical and immunochemical analyses confirm that saxiphilin is a unique protein that is distinct from bullfrog serum transferrin. The mechanism of (3H)STX binding to saxiphilin, including the pH-dependence and temperature-dependence, was characterized in detail. Recombinant saxiphilin was expressed in insect cells using a baculovirus vector and the STX-binding site was localized to the C-lobe domain of the protein. A phylogenetic survey found saxiphilin-like activity in arthropods, fish, amphibians and reptiles.

Descriptors :   *MARINE BIOLOGY, *CLONES, *SHELLFISH, *NEUROTOXINS, AMPHIBIANS, BIOCHEMISTRY, PROTEINS, EQUILIBRIUM(GENERAL), DEOXYRIBONUCLEIC ACIDS, FRESH WATER, CHEMICAL AGENTS, FUNCTIONAL ANALYSIS, ANTIDOTES, POISONING, LIVER, GENETIC ENGINEERING, BLOOD SERUM, FROGS, POTENCY, TOXINS AND ANTITOXINS, AMINO ACIDS, CNS DEPRESSANTS, NORTH AMERICA, BLOOD PLASMA, INSECTS, BLOOD PROTEINS, IMMUNOCHEMISTRY, PARALYSIS, ARTHROPODA, REPTILES.

Subject Categories : Biology
      Toxicology
      Biological Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE