Proteomic characterization of venom of the medically important Southeast Asian Naja sumatrana (Equatorial spitting cobra)

The proteome of Naja sumatrana (Equatorial spitting cobra) venom was investigated by shotgun analysis and a combination of ion-exchange chromatography and reverse phase HPLC. Shotgun analysis revealed the presence of 39 proteins in the venom while the chromatographic approach identified 37 venom proteins. The results indicated that, like other Asiatic cobra venoms, N. sumatrana contains large number of three finger toxins and phospholipases A₂, which together constitute 92.1% by weight of venom protein. However, only eight of the toxins can be considered as major venom toxins. These include two phospholipases A₂, three neurotoxins (two long neurotoxins and a short neurotoxin) and three cardiotoxins. The eight major toxins have relative abundance of 1.6–27.2% venom proteins and together account for 89.8% (by weight) of total venom protein. Other venom proteins identified include Zn-metalloproteinase-disintegrin, Thaicobrin, CRISP, natriuretic peptide, complement depleting factors, cobra venom factors, venom nerve growth factor and cobra serum albumin. The proteome of N. sumatrana venom is similar to proteome of other Asiatic cobra venoms but differs from that of African spitting cobra venom. Our results confirm that the main toxic action of N. sumatrana venom is neurotoxic but the large amount of cardiotoxins and phospholipases A₂ are likely to contribute significantly to the overall pathophysiological action of the venom. The differences in toxin distribution between N. sumatrana venom and African spitting cobra venoms suggest possible differences in the pathophysiological actions of N. sumatrana venom and the African spitting cobra venoms, and explain why antivenom raised against Asiatic cobra venom is not effective against African spitting cobra venoms.