Identification of tyrosine sulfation inConuspennaceus conotoxins α-PnIA and α-PnIB: further investigation of labile sulfo- and phosphopeptides by electrospray, matrix-assisted laser desorption/ionization (MALDI) and atmospheric pressure MALDI mass spectrometry
✍ Scribed by Wolfender, Jean-Luc; Chu, Feixia; Ball, Haydn; Wolfender, Florence; Fainzilber, Michael; Baldwin, Michael A.; Burlingame, Alma L.
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 163 KB
- Volume
- 34
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Liquid chromatography/electrospray ionization mass spectrometry was used to investigate the peptide composition of the venom of Conus pennaceus, a molluscivorous cone shell from the Red Sea. Based on observed this M r s, venom contained all known conotoxins previously isolated and identiÐed from this species. Interestingly, the doubly protonated species of only two of these conotoxins, a-PnIA and a-PnIB, showed additional related ions at + 40 m/z (+ 80 Da), indicating the presence of either sulfation or phosphorylation in both components. Highperformance liquid chromatographic (HPLC) fractions containing these two conotoxins were examined by matrixassisted laser desorption/ionization (MALDI) mass spectrometry in both positive and negative ion modes, as well as by MALDI high-energy collision-induced dissociation. These experiments established the presence of a single sulfated tyrosine residue within both a-PnIA and a-PnIB. Hence their post-translationally modiÐed sequences are (a-PnIA) and (a-PnIB). This assignment GCCSLPPCAANNPDY(S)C-NH 2 GCCSLPPCALSNPDY(S)C-NH 2 was supported by comparison of their mass spectral behavior with that of known sulfated and phosphorylated peptides. This data clariÐed further the distinguishing features of the ionization and fragmentation of such modiÐed peptides. Selective disulÐde folding of synthetic a-PnIB demonstrated that both sulfated and non-sulfated toxins co-elute on reversed-phase HPLC and that a-PnIB possesses the same disulÐde connectivity as other "classicalÏ a-conotoxins reported previously.