Structure and function of three types of phospholipase A_2 inhibitor s derived from the blood of venomous snakes

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1. Structure and function of PLIαWe have identified a PLIα-like protein, which showed about 70% sequence homology to Chinese mamushi PLIα but showed no iuhibitory activity from the serum of the non-venorilous striated snake and cloned its cDNA. We have constructed the recombinant chiineric proteins between the PLIα-like protein and Chinese mamushi PLIα and found that the sequence from 13 to 36 residues of Chinese mamushi PLIα were important for the bindihg and inhibition of the PLA_<2->. Furthermore, we found that the amino acid residues 26, 28, and 29 were especially important among this region. On the other hand, in order to determine the tertiary structure of PLIα, we searched for the best crystallization conditions of PLIα purified from the Chinese mamushi, serum, and we could obtain its needle crystal. However, the X-ray diffiaction image is not obtained yet.2. Structure and function of PLIαWe have identified PLIβ, which specifically inhibit group-II basic protein, from the serum of the striated snake, purified it, and cloned its cDNA. Alternatively, we are tying to establish the E. coli expression system for Chinese mamushi PLIβ. On the other hand, we searched for the best crystallization conditions of PLIβ purified from Chinese mamushi, serum, but we could not obtain the crystals suitable for X-ray crystallography by this time3. Structure and function of PLIγWe are investigating whether PLIγ could be reconstructed from the separated two subunits of Chinese mamushi PLIγ Without a loss of the inhibitory activity. On the other hand, we searched, for the best crystallization conditions of PLIγ purified from Chinese mamushi, serum, but we could not obtain the crystals suitable for X-ray crystallography by this time.