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

Toward a framework for sulfoproteomics: Synthesis and characterization of sulfotyrosine‐containing peptides

“…[51][52][53]147 Irrespective of the desorption/ionization method, it is generally observed that sulfoTyr residues are more stable in negative than in positive peptide ions, which indicates that deprotonation of the highly acidic sulfoester groups increases the activation energy required for fragmentation to occur. This observation can be explained on the basis of a hypothetical proton-induced fragmentation mechanism, which is similar to the mechanism proposed for the acid-catalyzed hydrolysis of sulfoTyr ( Figure 2A) in that it involves the formation of a labile zwitterion (ZI) as the key intermediate ( Figure 2C).…”

“…73 The analysis of monosulfated peptides by comparing positive and negative ion mass spectra is generally rather straightforward. 53,73,123,135,136,138,139,141 However, if multiple sulfoTyr residues are present in a peptide, complex fragmentation patterns are often observed, depending on the desorption/ioni- …”

“…50 Tyr sulfation also occurs in certain a-conotoxins that have been isolated from the venoms of various cone snail species and act as potent antagonists of neuronal nicotinic acetylcholine receptors. [51][52][53] While the majority of the known sulfoTyr-containing peptides are found in the animal kingdom, there are a few examples of Tyr sulfated plant peptides. For example, several sulfoTyr-containing growth factors, referred to as phytosulfokines (Table I), have been isolated from asparagus 54 and rice plants.…”

“…For example, Wolfender et al observed that the sulfated and non-sulfated versions of a-conotoxin PnIB co-eluted in RP-HPLC analysis. 53 Furthermore, Medzihradszky et al reported that several Ser/Thr sulfated peptides eluted later than the unmodified peptides. 129 Thus, it is evident that any conclusions drawn from RP-HPLC analysis have to be confirmed by other analytical techniques such as MS.…”

Sulfonation and Phosphorylation of Regions of the Dioxin Receptor Susceptible to Methionine Modifications

“…Thus, the mass shifts of 32 amu on the modified peptides resulted from post-translationally modified serine residues present in the peptides with accompanying chemically degraded methionines (51,52) rather than the presence of methionine sulfone. Various previous studies have reported that phosphorylated peptides preferentially display a neutral loss of 98 amu, whereas sulfonated serine residues exhibit a loss of a sulfono moiety (Ϫ80 amu) as a favored dissociation process (21,26,(53)(54)(55). The dominant neutral losses of 80 amu associated with these peptides indicated that serine residues 411 and 547 were sulfonated.…”