Identification of water-soluble selenium-containing proteins in selenized yeast by size-exclusion-reversed-phase HPLC/ICPMS followed by MALDI-TOF and electrospray Q-TOF mass spectrometry

J.R. Encinar (1) , Laurent Ouerdane (1) , W. Buchmann , J. Tortajada , Ryszard Lobinski (1) , J. Szpunar (1)

1 LCABIE - Laboratoire de Chimie Analytique Bio-Inorganique et Environnement

An approach to speciation of selenium incorporated in yeast proteins was developed. The tryptic digest of a water-soluble protein fraction isolated by size-exclusion chromatography was analyzed by reversed-phase HPLC/ ICPMS. The selenopeptides selected owing to the detector's elemental specificity were then analyzed by MALDI-TOFMS in order to select target ions for collision-induced dissociation MS. The latter, carried out with an electrospray Q-TOF spectrometer, enabled the sequencing of the selenopeptides detected by HPLC/ICPMS. The approach allowed for the first time the identification of a family of Se-containing proteins resulting from the replacement by selenomethionine of 2-9 methionine residues in a salt-stress-induced protein SIP18 (Mr 8874). The presence of these proteins was confirmed by MALDI-TOFMS of the original (nondigested) protein fraction. Another selenium protein identified was a heat-shock protein HSP12 (Mr 11 693) in which the only methionine residue was replaced by selenomethionine. These two Se-containing proteins accounted for more than 95% of selenium in the water-soluble protein fraction.

Domaines: Chimie analytique

J.R. Encinar, Laurent Ouerdane, W. Buchmann, J. Tortajada, Ryszard Lobinski, et al.. Identification of water-soluble selenium-containing proteins in selenized yeast by size-exclusion-reversed-phase HPLC/ICPMS followed by MALDI-TOF and electrospray Q-TOF mass spectrometry. Analytical Chemistry, 2003, 75 (15), pp.3765-3774. ⟨10.1021/ac034103m⟩. ⟨hal-00291356⟩