Natriuretic peptides are common components of reptile venoms and molecular cloning of their biosynthetic precursors has revealed that in snakes, they eo-encode bradykinin-potentiating peptides and in venomous lizards, some eo-encode bradykinin inhibitory peptides such as the helokinestatins. The common natriuretic peptide/helokinestatin precursor of the Gila Monster, Heloderma suspectum, encodes five helokinestatins of differing primary structures. Here we report the molecular cloning of a natriuretic peptide/helokinestatin precursor cDNA from a venom-derived cDNA library of the Mexican beaded lizard (Heloderma horridum) and the Gila Monster (Heloderma suspectum) and the structures of the novel peptides, helokinestatin-6, helokinestatin-7S and helokinestatin-7H, that have inhibitory effects on bradykinin responses in vascular smooth muscle. Snakes of the Elapidae and Viperidae families have evolved to produce venoms with specific well- defined modes of action that lead to prey immobilisation and ultimately death. The venoms of elapids contain neurotoxic components that attack both the peripheral and central nervous systems. In this project, dendrotoxin-K/I sequences from black mamba (Dendroaspis polylepis) venom were obtained, and these have inhibitory effects on the proteases, trypsin and chymotrypsin. The structures were obtained through use of a special primer in the 'shotgun cloning' of a venom- derived cDNA library. By this approach, the structure and precursor sequence of cardiotoxin-3 from the venom of the King Cobra, (Ophiophagus hannah) was also obtained. In contrast, viperid snake venoms contain components that are mainly haemorrhagic in nature or act upon the vascular system in other ways. Using the same molecular cloning strategy as adopted for elapid snakes, the structure of a novel C-type lectin was obtained from Puff Adder (Bitis arietans) venom and that of a novel PLA2 from the venom of the Cantil (Agkistrodon bilineatus).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:579787 |
| Date | January 2012 |
| Creators | Ma, Chengbang |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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