title: Crystal structure of a phospholipase A2from Bothrops asper venom: Insights into a new putative "myotoxic cluster".
abstract: Snake venoms from the Viperidae and Elapidae families often have several phospholipases A2(PLA2s), which may display different functions despite having a similar structural scaffold. These proteins are considered an important target for the development of drugs against local myotoxic damage because they are not efficiently neutralized by conventional serum therapy. PLA2s from these venoms are generally divided into two classes: (i) catalytic PLA2s (or Asp49-PLA2s) and (ii) non-catalytic PLA2-like toxins (or Lys49-PLA2s). In many Viperidae venoms, a subset of the basic Asp49-PLA2s displays some functional and structural characteristics of PLA2-like proteins and group within the same phylogenetic clade, but their myotoxic mechanism is still largely unknown. In the present study, we have crystallized and solved the structure of myotoxin I (MT-I), a basic myotoxic Asp49-PLA2isolated from Bothrops asper venom. The structure presents a dimeric conformation that is compatible with that of previous dimers found for basic myotoxic Asp49-PLA2s and Lys49-PLA2s and has been confirmed by other biophysical and bioinformatics techniques. This arrangement suggests a possible cooperative action between both monomers to exert myotoxicity via two different sites forming a putative membrane-docking site (MDoS) and a putative membrane disruption site (MDiS). This mechanism would resemble that proposed for Lys49-PLA2s, but the sites involved appear to be situated in a different region. Thus, as both sites are close to one another, they form a "myotoxic cluster", which is also found in two other basic myotoxic Asp49-PLA2s from Viperidae venoms. Such arrangement may represent a novel structural strategy for the mechanism of muscle damage exerted by the group of basic, Asp49-PLA2s found in viperid snake venoms.
authors.affiliation: Departamento de Física e Biofísica, Instituto de Biociências, UNESP - Univ. Estadual Paulista, Botucatu, SP, Brazil.
authors.forename: Guilherme H M
authors.initials: GH
authors.lastname: Salvador
authors.affiliation: Departamento de Física e Biofísica, Instituto de Biociências, UNESP - Univ. Estadual Paulista, Botucatu, SP, Brazil.
authors.forename: Juliana I
authors.initials: JI
authors.lastname: Dos Santos
authors.affiliation: Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica.
authors.forename: Bruno
authors.initials: B
authors.lastname: Lomonte
authors.affiliation: Departamento de Física e Biofísica, Instituto de Biociências, UNESP - Univ. Estadual Paulista, Botucatu, SP, Brazil. Electronic address: fontes@ibb.unesp.br.
authors.forename: Marcos R M
authors.initials: MR
authors.lastname: Fontes
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D017837:Bothrops; D003435:Crotalid Venoms / Q000737:chemistry / Q000201:enzymology* / Q000633:toxicity; D018360:Crystallography, X-Ray; D054501:Group II Phospholipases A2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D006801:Humans; D018482:Muscle, Skeletal / Q000737:chemistry / Q000187:drug effects; D054467:Phospholipases A2 / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity; D010802:Phylogeny; D030162:Reptilian Proteins / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity
chemical_list: D003435:Crotalid Venoms; D030162:Reptilian Proteins; D054501:Group II Phospholipases A2; D054467:Phospholipases A2; C076780:myotoxin I
keywords: Myototins; Myotoxic mechanism; Phospholipase A(2); Snakebite envenomation; Viperidae venoms