Disintegrins of Crotalus simus tzabcan venom: Isolation, characterization and evaluation of the cytotoxic and anti-adhesion activities of tzabcanin, a new RGD disintegrin

Disintegrins are small non-enzymatic proteins common in the venoms of many viperid snakes. These proteins have received significant attention due to their ability to inhibit platelet aggregation and cell adhesion, making them model compounds in drug development and design investigations. The present study used a combination of molecular and proteomic techniques to screen the venom of the Middle American Rattlesnake (Crotalus simus tzabcan) for novel disintegrins. Six disintegrin isoforms were identified, and the most abundant, named tzabcanin, was further isolated and characterized. Tzabcanin consists of 71 amino acids, has a mass of 7105 Da (by MALDI-TOF mass spectrometry) and contains the canonical RGD binding domain. Tzabcanin was not cytotoxic to MCF-7 cells but showed weak cytotoxicity to Colo-205 cells following a 24 h incubation period. Tzabcanin inhibited cell adhesion of both cell lines to immobilized fibronectin and vitronectin, and cell adhesion to immobilized tzabcanin was inhibited when cells were incubated with a cation chelator (EDTA), indicating that integrin-tzabcanin binding is specific. This study provides a detailed analysis of the purification and characterization of tzabcanin and provides sequence and mass data for the multiple disintegrins present in the venom of C. s. tzabcan.