In vitro: |
J. Biol. Chem., 1996, 271(30):17785-90. | Variabilin, a Novel RGD-containing Antagonist of Glycoprotein IIb-IIIa and Platelet Aggregation Inhibitor from the Hard Tick Dermacentor variabilis*[Reference: WebLink] | METHODS AND RESULTS:
A novel inhibitor of human platelet aggregation, named variabilin, was isolated from salivary glands of the hard tick Dermacentor variabilis using a combination of gel filtration and high pressure liquid chromatography. Variabilin was a potent antagonist of the fibrinogen receptor glycoprotein IIb-IIIa (GPIIb-IIIa; αIIbβ3) and the vitronectin receptor αvβ3. Amino acid sequence analysis by Edman degradation revealed that it has 47 residues, with a molecular weight of 4968.5. Like many other naturally occurring antagonists of GPIIb-IIIa, variabilin contains the RGD (Arg-Gly-Asp) motif. However, unlike the RGD-containing antagonists of GPIIb-IIIa, the RGD sequence of variabilin is not positioned in a loop bracketed by cysteine residues.
CONCLUSIONS:
It has little sequence homology to the other known naturally occurring antagonists of GPIIb-IIIa, including the disintegrins from snakes, decorsin and ornatin from leeches, and disagregin from soft ticks. Variabilin is the first RGD-containing antagonist isolated from ticks. |
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