Crystal structure determination of alkaline haemorrhagin AaH III from snake venom of Agkistrodon acutus.

The haemorrhagin AaH III isolated from the snake venom of Agkistrodon acutus is one of the few alkaline ones in snake venoms. Its crystals belong to space group P2(1)2(1)2(1) with a = 9. 573 4 nm, b = 4. 996 7 nm and c = 4.728 8 nm. Its crystal structure was determined by the molecular replacement method according to the model of metalloproteinase Adamalysin II from eastern rattlesnake venom. The AaH III structure has been refined by PROLSQ. The final R factor was 0.254 and the RMS deviations of bond lengths and angles were 0.001 8 nm and 1.5 degrees . The structure comparison suggested that AaH III has a similar structure to other snake venom zinc-metalloproteinases. They all belong to matrix metalloproteinases super-family.