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RE: Heloderma venom evolution
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by lanceheads on February 1, 2010
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Bryan,
I am awaiting any further work on Desmodia. Have you got anything yet?
Thanks,
Randal Berry
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RE: Heloderma venom evolution
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by BGF on February 1, 2010
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In progress. It'll be a while before the vampires see the light of day (pun fully intended :) )
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RE: Heloderma venom evolution
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by nietzsche on February 2, 2010
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Can anyone who has read this article point out to me where they state the reasons for favoring a glucagon-like ancestor for the exendins, rather than a VIP? I keep reading and re-reading and I can not find it. I am somehow missing it.
Help me Obi wan Kenobi..........Thanks,
Kelly
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RE: Heloderma venom evolution
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by BGF on February 2, 2010
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Key passage is ".....Endogenous VIP hormones have been shown to be more potent vasodilators than endogenous glucagon hormones (Ezawa, Oota, and Saitou 2006). As a consequence, a peptide that mimics a generalized VIP hormone may provide a more effective toxin. The results of this study demonstrate that exendin-1 and -2 have a higher cardioactivity than exendin-3 and -4 and also the non-toxin peptide GLP-1 (O12956) (Figure 6A,B). This is in agreement with other studies on exendin-1 and -2 which demonstrated vasodialatory actions similar to VIP (Uddman et al. 1999; Tsueshita et al. 2004). The molecular evolution from a less potent (glucagon-like) form towards a more potent (VIP-like) form is more plausible than the converse. The origin of exendin peptides thus favours a glucagon-like ancestor with subsequent divergence of one duplicate to convergently become a VIP-like toxin (Figures 8B’ or 8C’). "
We have a new paper under review where we have indeed confirmed the glucagon ancestry, the relative presence of the different insoforms in the two species and thus the timing of divergence between the two classes of exendin toxins :)
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