Blood coagulation is a highly specialized process that is required to prevent blood loss following vascular damage. Central to the formation of a blood clot are the blood coagulation proteins... Show moreBlood coagulation is a highly specialized process that is required to prevent blood loss following vascular damage. Central to the formation of a blood clot are the blood coagulation proteins factor V and factor X. Aside from preventing blood loss, the coagulation system can also be exploited to gain selective advantages. The procoagulant venom of the Australian Elapid snakes comprises a powerful prothrombin-activating enzyme complex consisting of FV- and FX-like proteins that are specifically expressed in the venom gland. These coagulation proteins have evolved into potent toxins due to some remarkable gain-of-function adaptations that enable this prothrombinase-like complex to initiate coagulation in an uncontrolled manner. In this thesis, we focus on the unique evolutionary adaptations of the P. textilis venom derived proteins v-ptFV and v-ptFX. By using biochemical approaches, we assess the structure-function relationships of several uniquely modified structural elements Show less
The explosive radiation and diversification of the advanced snakes (superfamily Colubroidea) was associated with changes in all aspects of the shared venom system. Morphological changes included... Show moreThe explosive radiation and diversification of the advanced snakes (superfamily Colubroidea) was associated with changes in all aspects of the shared venom system. Morphological changes included the partitioning of the mixed ancestral glands into two discrete glands devoted for production of venom ormucous respectively, as well as changes in the location, size and structural elements of the venom-delivering teeth. Evidence also exists for homology among venom gland toxins expressed across the advanced snakes. However, despite the evolutionary novelty of snake venoms, in-depth toxin molecular evolutionary history reconstructions have been mostly limited to those types present in only two front-fanged snake families, Elapidae and Viperidae. To have a broader understanding of toxins shared among extant snakes, here we first sequenced the transcriptomes of eight taxonomically diverse rear-fanged species and four key viperid species and analysed major toxin types shared across the advanced snakes. Show less
The venom of the Australian snake Pseudonaja textilis contains coagulation factors V (five) and X (ten) which have been adapted to derail the blood clotting system of its prey. Snake venom factor V... Show moreThe venom of the Australian snake Pseudonaja textilis contains coagulation factors V (five) and X (ten) which have been adapted to derail the blood clotting system of its prey. Snake venom factor V is unique in that is constitutively active, unlike its human counterpart. The snake liver transcriptome was found to contain alternatively spliced factor V mRNA that encoded for either the activated protein or its quiescent form. A potential pre-mRNA splicing mechanism was uncovered that may yield the active protein. Snake venom factor V is also particularly stable due to several modifications to its molecular structure. These modifications have been investigated in detail by engineering chimeras of human and snake venom factor V. The snake venom factor X molecule was also investigated in more detail. It was discovered that this enzyme is insensitive to the action of certain anticoagulant drugs (Factor Xa inhibitors) due to a unique molecular modification. A Human factor X can be modified in similar fashion, so that it is no longer sensitive to the action of Factor Xa inhibitors. This finding could make an important contribution to acute care for patients who experience life-threatening bleeding after the use of FXa inhibitors. Show less