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esearch 47ADJUNCT SCIENTISTSBarbara C. FurieBruce FurieLeisa StenbergVISITING SCIENTISTJohan Stenflo, Universityof Lund, SwedenASSISTANT RESEARCHSCIENTISTMark BrownPublicationBrown, MA; Begley, GS;Czerwiec, E; Stenberg,LM; Stenflo, J; Jacobs, M;Kalume, DE; Roepstorff, P;Furie, BC; Furie, B. 2005.Precursors of novel Glacontainingconotoxinscontain a carboxy-terminalrecognition site thatdirects γ−carboxylation.Biochemistry 44: 9150-9159.laboratory of barbara furie and bruce furieγ−Carboxyglutamic acid is a calcium-binding amino acid that isfound in the conotoxins of the cone snail, Conus. This laboratoryinvestigates the vitamin K-dependent biosynthesis of this aminoacid in Conus and other marine invertebrates. This satellitelaboratory relates closely to the main laboratory, the Center forHemostasis and Thrombosis, at Harvard Medical School in Boston.The marine cone snail is the sole invertebrate known to containthe vitamin K-dependent amino acid, γ−carboxyglutamic acid(Gla). This amino acid is found in conotoxins within its venom.During the past year, we have proven that γ−carboxylation is aposttranslational process and not a cotranslational process. Novelconotoxins containing γ−carboxyglutamicacid were cloned, and found to have acarboxylation recognition site downstreamof the target glutamic acids instead of theusual upstream site within the codingregion of the propeptide.We have cloned and compared theγ−glutamyl carboxylase from vertebratesand invertebrates—the enzyme required tosynthesize γ-carboxyglutamic acid—anddemonstrated marked sequence similaritydespite evolutionary divergence over500 million years ago. These resultsdemonstrate the vitamin K-dependentbiosynthesis of Gla is a highly conserved function in the animalkingdom. To identify novel Gla containing proteins conservedin animal species, we are identifying novel vitamin K-dependentproteins in invertebrates and hemichordates.