Structure Determination
of Basic Phospholipase A2 from the Venom of Agkistrodon
halys Pallas in A New Monoclinic Crystal Form
ZHAO Ke-Hao, CHAI Xiao-Mei, SONG Shi-Ying, LIN Zheng-Jiong*
( National Laboratory of Biomacromolecules, Institute of Biophysics, the
Chinese Academy of Sciences, Beijing 100101, China )
ZHOU Yuan-Cong
( Shanghai Institute of Biochemistry, the Chinese Academy of Sciences,
Shanghai 200031, China )
Abstract Basic phospholipase
A2 from the venom of Agkistrodon halys Pallas (Agkistrodin
blomhoffii brevicaudus) exhibits hemolytic and anti-coagulant activities.
A new monoclinic crystal form with four molecules per asymmetric unit was grown
in the absence of n-octyl β-o-glucopyranoside (β-OG). The
enzyme structure was determined by the molecular replacement method. The
combined analysis of self- and cross- rotation function was used and
non-crystallographic symmetry restraints were imposed to the structure
refinement. The final model gave an acceptable crystallographic R
factor and reasonable stereochemistry. Two molecules formed an
interfacial-recognition-site linked dimer and two such dimers constituted a
tetramer having pseudo 222 symmetry. Structural comparison with previously
reported monoclinic forms, in which β-OG was bound, showed that the variation
of crystallization conditions had effects on the crystal packing, leading to
significant changes of the cell parameters. Nevertheless, the structures of
both the dimer and tetramer in the two crystal forms closely resembled to each
other, indicating that the oligomers found in the monoclinic crystal forms were
stable.
Key words venom phospholipase A2； X-ray crystallography； three-dimentional structure； oligomer
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