BaG, a new dimeric metalloproteinase/disintegrin from the Bothrops alternatus snake venom that interacts with α5β1 integrin

The α5β1 integrin is one of the major fibronectin receptors which plays an essential role in the adhesion of normal and tumor cells to extracellular matrix. Here, we describe the isolation and characterization of a novel dimeric metalloproteinase/disintegrin, which is an inhibitor of fibronectin binding to the α5β1 integrin. This protein (BaG) was isolated from the venom of the South American snake Bothrops alternatus by gelatin–Sepharose affinity and anion exchange chromatography. The molecular mass of BaG was approximately 130 kDa under non-reducing conditions and 55 kDa under reducing conditions by SDS–PAGE. BaG shows proteolytic activity on casein that was inhibited by EDTA. 1,10-phenanthroline-treated BaG (BaG-I) inhibits ADP-induced platelet aggregation with an IC50 of 190 nM. BaG-I inhibits fibronectin-mediated K562 cell adhesion with an IC50 of 3.75 μM. K562 cells bind to BaG-I probably through interaction with α5β1 integrin, since anti-α5β1 antibodies inhibited K562 cell adhesion to BaG-I. In addition, BaG-I induces the detachment of K562 cells that were bound to fibronectin. In summary, we have purified a novel, dimeric snake venom metalloproteinase/disintegrin that binds to the α5β1 integrin.