This 41-residue disintegrin (FW = 4401 g/mol; Sequence CTTGPCCRQ CKLKPAGTTCWKTSLTSHYCTGKSCDCPLYPG, with disulfide bonds at Cys1-Cys10, Cys6-Cys29, Cys7-Cys34, and Cys19-Cys36) from the venom of the blunt-nosed viper Vipera lebetina obtusa exhibits tight binding to integrins, inhibiting platelet aggregation, IC50 = 2 nM. It is the shortest polypeptide to contain an integrin-recognition loop. Target(s): Obtustatin is a highly potent integrin α1β1 inhibitor (IC50 = 0.8 nM for α1β1 binding to type IV collagen), displaying specificity for α1β1 over α2β1, αIIbβ3, αvβ3, α4β1, α5β6, α9β1 and α4β7.
