title: Electrospray ionization quadrupole time-of-flight and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometric analyses to solve micro-heterogeneity in post-translationally modified peptides from Phoneutria nigriventer (Aranea, Ctenidae) venom.
abstract: Previous studies of the fractionated venom of the Brazilian armed spider Phoneutria nigriventer, obtained by gel filtration, have demonstrated the presence of a fraction PhM, a pool of small peptides (up to 2000 Da) that provoke contractions in smooth muscle of guinea pig ileum. Initial attempts to sequence these peptides were largely unsuccessful because of the low purification yield and the fact that the majority seemed to be blocked at their N-termini. In the present work, analysis of this venom fraction by mass spectrometry has revealed the existence of a highly complex mixture of peptides with molecular weights corresponding to those observed for the muscle-active peptides previously described (800-1800 Da). These peptides appear to be a family of isoforms with some particular features. The amino acid sequences of 15 isoforms have been determined by tandem mass spectrometry (MS/MS) using both electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q/ToFMS) and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-ToF/ToFMS). These molecules contain post-translational modifications such as proteolysis and C-terminal amidation, which combine to generate additional isoforms. All the isoforms sequenced in this study possess an N-terminal pyroglutamic acid residue. A search for sequence similarities with other peptides in databanks revealed that these peptides are structurally related to the tachykinins, a family of neuro-hormone peptides. The data obtained in this study will be essential for the subsequent steps of this research, the synthesis of these peptides and pharmacological characterization of their biological activity.
authors.affiliation: Núcleo de Biomoléculas, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, 31270-901, Belo Horizonte, MG, Brazil. apimenta@icb.ufmg.br
authors.forename: Adriano M C
authors.initials: AM
authors.lastname: Pimenta
authors.forename: Breno
authors.initials: B
authors.lastname: Rates
authors.forename: Carlos
authors.initials: C
authors.lastname: Bloch
authors.forename: Paulo C
authors.initials: PC
authors.lastname: Gomes
authors.forename: Marcelo M
authors.initials: MM
authors.lastname: Santoro
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: de Lima
authors.forename: Michael
authors.initials: M
authors.lastname: Richardson
authors.forename: Marta do N
authors.initials: Mdo N
authors.lastname: Cordeiro
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D009842:Oligopeptides / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013111:Spider Venoms / Q000737:chemistry*; D013112:Spiders
chemical_list: D009842:Oligopeptides; D013111:Spider Venoms