Crystal Structure OF A BASIC MYOTOXIC Phospholipase A₂ homologue from the Bothropsneuwiedi pauloensis Venom 

MAGRO, A.J.(1), SOARES, A.M.(2), GIGLIO, J.R.(3), FONTES, M.R.M.(1)

(1)Departamento de Física e Biofísica, Instituto de Biociências da UNESP, Botucatu, (2)Departamento de Biotecnologia, UNAERP, Ribeirão Preto, (3)Departamento de Bioquímica, Faculdade de Medicina de Ribeirão Preto, USP, Ribeirão Preto.

In Latin America the most of the ophidian accidents are caused by snakes of the genus Bothrops. In addition to systemic alterations, these poisonings are characterized by prominent local tissue damage due to myonecrosis, hemorrhage and edema. Acute muscle damage induced by these venoms is due mainly two basic myotoxicphospholipasesA2 (PLA₂). Its members seem to fall in two categories: enzymatically-active PLA₂ (Asp49) and enzymatically-inactive PLA₂ (Lys49). Myotoxins are believed to act on the sarcoplasma membrane, thus inducing a disorganization of the phospholipds, the loss of intracellular components and an influx of Ca⁺⁺ ions, however, in the case of Lys49 PLA₂ is not still completely understood the myotoxic mechanism. We recently studied B. neuwiedi venoms from different regions and observed two basic myotoxins found only on B. neuwiedi pauloensis of the region of Botucatu, SP. The BnSP-7 was cDNA cloned and sequenced and several biological activities were assayed and compared with those of chemically modified toxin involving specific residues. In this work we show the X-ray structure determination, refinement process and structural characteristics of BnSP-7. The toxin was crystallized and data collection was made using synchrotron radiation at LNLS (Campinas). The crystals belong to the space group P3₁21with cell constants a=b=58.2and c=132.0Å. Data was collected up to 2.3 Å resolution. The dimeric toxin structure was solved by Molecular Replacement method and is currently being refined using the CNS program.  The structure has excellent geometry and electronic density map.

CORRESPONDENCE TO:

AngeloJosé Magro, Departamento de Física e Biofísica, IB, UNESP, Caixa Postal 510, Botucatu, SP, CEP: 18618-000, Email: angelomagro@zipmail.com.br