Purification, partial characterization and crystallization of acucetin, a protein containing both disintegrin-like and cysteine-rich domains released by auto-proteolysis of a P-III-type metalloproteinase AaH-IV from Agkistrodon acutus venom

AaH-IV, a P-III-type metalloproteinase found in Agkistrodon acutus venom, readily cleaves itself to release a stable protein named acucetin at 310 K under neutral and weakly alkaline conditions. A partial amino-acid residue sequence of acucetin indicates that the protein has a high homology to snake-venom proteins containing both disintegrin-like and cysteine-rich domains. Acucetin has been crystallized in space group R32, with hexagonal unit-cell parameters a = b = 155.98, c = 76.07 Å. The V_M value of about 2.97 Å³ Da^-1 suggests the presence of only one molecule in the asymmetric unit.