title: Structure of agkistrodotoxin in an orthorhombic crystal form with six molecules per asymmetric unit.
abstract: The structure of agkistrodotoxin crystallized under basic conditions has been determined at 2.8 A resolution by the molecular-replacement technique and refined to a crystallographic R factor of 0.194 and a free R factor of 0.260 with good stereochemistry. The molecular packing in the crystal differs from other PLA(2)s. The six molecules in the asymmetric unit form three dimers linked by Ca(2+) ions in a near-perfect six-ligand octahedral coordinating system. Extensive intermolecular hydrophobic interactions occur at the interfacial recognition site of each neurotoxin molecule, which provides an insight into phospholipase A(2)-membrane interactions. This hydrophobic interaction-induced molecular association along the interfacial recognition site suggests a self-protection mechanism of agkistrodotoxin.
authors.affiliation: National Laboratory of Biological Macromolecules, Institute of Biophysics, Academia Sinica, Beijing 100101, People's Republic of China.
authors.forename: L
authors.initials: L
authors.lastname: Tang
authors.forename: Y C
authors.initials: YC
authors.lastname: Zhou
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Lin
mesh_terms: D017836:Agkistrodon; D000818:Animals; D002118:Calcium / Q000737:chemistry; D003435:Crotalid Venoms / Q000737:chemistry* / Q000302:isolation & purification; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D008958:Models, Molecular; D009498:Neurotoxins / Q000737:chemistry* / Q000302:isolation & purification; D020836:Protein Structure, Quaternary
chemical_list: D003435:Crotalid Venoms; D009498:Neurotoxins; C054663:alpha-agkistrodotoxin; D002118:Calcium