Detection of vitamin K-dependent proteins in venoms with a monoclonal antibody specific for gamma-carboxyglutamic acid

摘要

gamma-Carboxyglutamic acid (Gla) is tin unusual amino acid that is synthesized post-translationally from glutamate in a vitamin K-dependent reaction, The dicarboxylic side chain of Gla chelates Ca2+, a property important for the biological activity of vitamin K-dependent proteins. To date, Gla-containing polypeptides have been identified in venom from two groups of organisms: clapid snakes, and snails of the genus Conus, In certain elapid snakes, a gamma-carboxylated coagulation factor Xa-like protein is a component of the venom whereas cone snails utilize Gla in a range of peptide neurotoxins. Using a monoclonal antibody that specifically recognizes Gla residues, venom samples from various organisms were screened by western blotting and immunofluorescence assays. Amino acid analyses were also performed on most samples. A survey of 21 snake species from 12 genera detected gamma-carboxylated polypeptides, only in venom of snakes from the elapid subfamily Acanthophiinae. Gla-containing polypepticles were also observed in cone snail venom but not in venom or toxic salivary secretions from several other organisms. The Gla-specific antibody used here provides, a simple immunochemical means to detect gamma-carboxylated polypeptide,, in venom and may allow new species to be identified that utilize Gla in the biosynthesis of toxic polypeptides.