title: How C-terminal carboxyamidation alters the biological activity of peptides from the venom of the eumenine solitary wasp.
abstract: Inflammatory peptides display different types of post-transcriptional modifications, such as C-terminal amidation, that alter their biological activity. Here we describe the structural and molecular dynamics features of the mast cell degranulating peptide, eumenine mastoparan-AF (EMP-AF-NH(2)), found in the venom of the solitary wasp, and of its carboxyl-free C-terminal form (EMP-AF-COO(-)) characterized by a reduced activity. Circular dichroism indicates that both peptides switch from a random coil conformation in water to a helical structure in TFE and SDS micelles. NMR data, in 30% TFE, reveal that the two peptides fold into an alpha-helix spanning most of their length, while they differ in terms of molecular rigidity. To understand the origins of the conformational flexibility observed in the case of EMP-AF-COO(-), a 5 ns MD simulation was carried out for each peptide, in an explicit water/TFE environment. The results show that the two peptides differ in an H-bond between Leu14 NH(2) and the backbone carbonyl of Ile11. The loss of that H-bond in EMP-AF-COO(-) leads to a significant modification of its structural dynamics. In fact, as evidenced by essential dynamics analysis, while EMP-AF-NH(2) exists mainly as a rigid structure, EMP-AF-COO(-) presents two helical stretches that fluctuate in some sort of independent fashion. We conclude that the diverse biological activity of the two peptides is not simply due to the reduction of the net positive charge, as generally suggested, but also to a structural perturbation of the amphipathic alpha-helix that affects their ability to perturb the cell membrane.
authors.affiliation: Center for Structural Molecular Biology, BioNMR Laboratory, LNLS, Campinas, SP, Brazil.
authors.forename: Maurício L
authors.initials: ML
authors.lastname: Sforça
authors.forename: Sérgio
authors.initials: S
authors.lastname: Oyama
authors.forename: Fernanda
authors.initials: F
authors.lastname: Canduri
authors.forename: Carla C B
authors.initials: CC
authors.lastname: Lorenzi
authors.forename: Thelma A
authors.initials: TA
authors.lastname: Pertinhez
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Konno
authors.forename: Bibiana M
authors.initials: BM
authors.lastname: Souza
authors.forename: Mário S
authors.initials: MS
authors.lastname: Palma
authors.forename: J
authors.initials: J
authors.lastname: Ruggiero Neto
authors.forename: Walter F
authors.initials: WF
authors.lastname: Azevedo
authors.forename: Alberto
authors.initials: A
authors.lastname: Spisni
mesh_terms: D000577:Amides / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D002942:Circular Dichroism; D003198:Computer Simulation; D019476:Insect Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014270:Trifluoroethanol / Q000737:chemistry; D014862:Wasp Venoms / Q000737:chemistry / Q000378:metabolism*; D014867:Water / Q000737:chemistry
chemical_list: D000577:Amides; D019476:Insect Proteins; D010446:Peptide Fragments; D014862:Wasp Venoms; C412288:eumenine mastoparan-AF; D014867:Water; D014270:Trifluoroethanol