Conformational study of a new SGTx1 neurotoxin from the spider Scodra griseipes using mass spectrometry.
SGTx1 is a new neurotoxin from the venom of Scodra griseipes. Because of the small quantity of this natural peptide available, mass spectrometry was used to obtain information on its higher-order structure. The kinetics of reduction by 1,4-dithiothreitol (DTT) was monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), and showed that one of the three disulfide bridges was appreciably more accessible to the DTT. Studies based on the charge state distribution (CSD) and H/D exchange of the non-reduced peptide, under neutral and acidic conditions, were performed using electrospray mass spectrometry (ES-MS). In neutral solution, SGTx1 showed a maximum charge state of four compared with seven potentially protonated basic residues, and all labile hydrogens were exchanged. However, under acidic conditions, a maximum charge state of only five was observed, and four of the labile hydrogens could not be deuterated. These observations are interpreted in terms of a rigid structure maintained by the disulfide bridges, which can be temporarily relaxed by disulfide bridge scrambling only at higher pH values.
Marvin
L
L
Spectrométrie de Masse Bio-Organique, CNRS-UPRESA 6014, INSERM-IFR23, UFR des sciences, Université de Rouen, 76821 Mont Saint Aignan-Cedex, France.
Lange
C
C
D000595:Amino Acid Sequence; D004220:Disulfides / Q000032:analysis; D004229:Dithiothreitol; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000737:chemistry*; D011487:Protein Conformation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013111:Spider Venoms / Q000737:chemistry*; D013439:Sulfhydryl Reagents
D004220:Disulfides; D007202:Indicators and Reagents; D009498:Neurotoxins; C400227:SGTx1 toxin; D013111:Spider Venoms; D013439:Sulfhydryl Reagents; D004229:Dithiothreitol