title: High molecular weight components of the injected venom of fish-hunting cone snails target the vascular system.
abstract: The venom of marine cone snails is a rich source of pharmacotherapeutic compounds with striking target specificity and functional diversity. Small, disulfide-rich peptide toxins are the most well characterized active compounds in cone snail venom. However, reports on the presence of larger polypeptides have recently emerged. The majority of these studies have focused on the content of the dissected venom gland rather than the injected venom itself. Recent breakthroughs in the sensitivity of protein and nucleotide sequencing techniques allow for the exploration of the proteomic diversity of injected venom. Using mass spectrometric analysis of injected venoms of the two fish-hunting cone snails Conus purpurascens and Conus ermineus, we demonstrate the presence of angiotensin-converting enzyme-1 (ACE-1) and endothelin converting enzyme-1 (ECE-1), metalloproteases that activate potent vasoconstrictive peptides. ACE activity was confirmed in the venom of C. purpurascens and was significantly reduced in venom preincubated with the ACE inhibitor captopril. Reverse-transcription PCR demonstrated that these enzymes are expressed in the venom glands of other cone snail species with different prey preferences. These findings strongly suggest that cone snails employ compounds that cause disruption of cardiovascular function as part of their complex envenomation strategy, leading to the enhancement of neurotropic peptide toxin activity.
  
  
  CONCLUSIONS
  To our knowledge, this is the first study to show the presence of ACE and ECE in the venom of cone snails. Identification of these vasoactive peptide-releasing proteases in the injected venoms of two fish-hunting cone snails highlights their role in envenomation and enhances our understanding of the complex hunting strategies utilized by these marine predators. Our findings on the expression of these enzymes in other cone snail species suggests an important biological role of ACE and ECE in these animals and points towards recruitment into venom from general physiological processes.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 3010 Victoria, Australia. Electronic address: safavihelena@gmail.com.
authors.forename: Helena
authors.initials: H
authors.lastname: Safavi-Hemami
authors.forename: Carolina
authors.initials: C
authors.lastname: Möller
authors.forename: Frank
authors.initials: F
authors.lastname: Marí
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Purcell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D002319:Cardiovascular System / Q000187:drug effects; D052078:Conus Snail / Q000201:enzymology*; D018076:DNA, Complementary / Q000378:metabolism; D000072396:Endothelin-Converting Enzymes; D006863:Hydrogen-Ion Concentration; D008666:Metalloendopeptidases / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D008978:Mollusk Venoms / Q000201:enzymology*; D010455:Peptides / Q000378:metabolism; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D040901:Proteomics; D017386:Sequence Homology, Amino Acid; D014661:Vasoconstriction
chemical_list: D018076:DNA, Complementary; D008978:Mollusk Venoms; D010455:Peptides; D007703:Peptidyl-Dipeptidase A; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D000072396:Endothelin-Converting Enzymes
keywords: Angiotensin-converting enzyme; Cone snails; Endothelin-converting enzyme; Injected venom; Vasoconstriction