title: Crystal structure of a novel myotoxic Arg49 phospholipase A2 homolog (zhaoermiatoxin) from Zhaoermia mangshanensis snake venom: insights into Arg49 coordination and the role of Lys122 in the polarization of the C-terminus.
abstract: The venom of Zhaoermia mangshanensis, encountered solely in Mt Mang in China's Hunan Province, exhibits coagulant, phosphodiesterase, l-amino acid oxidase, kallikrein, phospholipase A2 and myotoxic activities. The catalytically inactive PLA2 homolog referred to as zhaoermiatoxin is highly myotoxic and displays high myonecrotic and edema activities. Zhaoermiatoxin possesses a molecular weight of 13,972Da, consists of 121 amino-acid residues cross-linked by seven disulfide bridges and shares high sequence homology with Lys49-PLA2s from the distantly related Asian pitvipers. However, zhaoermiatoxin possesses an arginine residue at position 49 instead of a lysine, thereby suggesting a secondary Lys49-->Arg substitution which results in a catalytically inactive protein. We have determined the first crystal structure of zhaoermiatoxin, an Arg49-PLA2, from Zhaoermia mangshanensis venom at 2.05 angstroms resolution, which represents a novel member of phospholipase A2 family. In this structure, unlike the Lys49 PLA2s, the C-terminus is well ordered and an unexpected non-polarized state of the putative calcium-binding loop due to the flip of Lys122 towards the bulk solvent is observed. The orientation of the Arg-49 side chain results in a similar binding mode to that observed in the Lys49 PLA2s; however, the guadinidium group is tri-coordinated by carbonyl oxygen atoms of the putative calcium-binding loop, whereas the Nzeta atom of lysine is tetra-coordinated as a result of the different conformation adopted by the putative calcium-binding loop.
authors.affiliation: Center for Structural & Molecular Biology, Department of Physics, IBILCE/UNESP, R. Cristovao Colombo 2265, São José do Rio Preto, São Paulo CEP 15054-000, Brazil.
authors.forename: Mário T
authors.initials: MT
authors.lastname: Murakami
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kuch
authors.forename: Christian
authors.initials: C
authors.lastname: Betzel
authors.forename: Dietrich
authors.initials: D
authors.lastname: Mebs
authors.forename: Raghuvir K
authors.initials: RK
authors.lastname: Arni
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000838:Anions / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003435:Crotalid Venoms / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D054467:Phospholipases A2 / Q000737:chemistry* / Q000378:metabolism; D011092:Polyethylene Glycols / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment; D017819:Viperidae / Q000502:physiology*
chemical_list: D000838:Anions; D003435:Crotalid Venoms; D011092:Polyethylene Glycols; D054467:Phospholipases A2; D002118:Calcium