title: Crystal structure of a phospholipase A(2) homolog complexed with p-bromophenacyl bromide reveals important structural changes associated with the inhibition of myotoxic activity.
abstract: For the first time, the structure of a catalytic inactive phospholipase A(2) homolog (Lys49-PLA(2)s) complexed with p-bromophenacyl bromide (BPB) has been solved by X-ray crystallography. Lys49-PLA(2)s are among the main components of Viperidae snake venoms, causing myonecrosis and other actions despite their catalytic inactivity. BPB, a classic inhibitor of catalytic-active PLA(2)s, has been used since the 1970s because it binds specifically the His48 residue of the catalytic site. Curiously, when Lys49-PLA(2) is chemically modified by BPB, it causes a partial inhibition of the myotoxic function which is associated with the C-terminus and not with the catalytic site. The structure of PrTX-I complexed to BPB revealed unambiguously that the inhibitor binds covalently to His48, causing a distortion of the Ca(2)(+)-binding loop region and C-terminus rearrangement in one of its monomers. The comparison between the apo and BPB-complexed PrTX-I structures showed an increased symmetry between the two monomers with the formation of an interchain hydrogen bond between Tyr119 residues. PrTX-I undergoes tertiary and quaternary structural changes when complexed to BPB which could be related to reduction of myotoxicity and other toxic activities. We also proposed a novel myotoxic inhibition hypothesis integrating "myotoxic" and "active" sites for bothropic Lys49-PLA(2)s.
authors.affiliation: Departamento de Física e Biofísica, Instituto de Biociências, UNESP, Distrito de Rubião Jr., Caixa Postal 510, 18618-000, Botucatu-SP, Brazil.
authors.forename: Daniela P
authors.initials: DP
authors.lastname: Marchi-Salvador
authors.forename: Carlos A H
authors.initials: CA
authors.lastname: Fernandes
authors.forename: Lucas B
authors.initials: LB
authors.lastname: Silveira
authors.forename: Andreimar M
authors.initials: AM
authors.lastname: Soares
authors.forename: Marcos R M
authors.initials: MR
authors.lastname: Fontes
mesh_terms: D000098:Acetophenones / Q000737:chemistry; D000818:Animals; D017837:Bothrops; D003435:Crotalid Venoms / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D008239:Lysine / Q000737:chemistry; D008958:Models, Molecular; D064801:Phospholipase A2 Inhibitors; D054467:Phospholipases A2 / Q000737:chemistry*; D011487:Protein Conformation; D055503:Protein Multimerization
chemical_list: D000098:Acetophenones; D003435:Crotalid Venoms; D064801:Phospholipase A2 Inhibitors; D054467:Phospholipases A2; D008239:Lysine; C006821:4-bromophenacyl bromide