Se-Hg Dual-element Labeling Strategy for Selectively Recognizing Selenoprotein and Selenopeptide

Abstract

An endogenous element-label plus exogenous element-tag strategy was proposed for inductively coupled plasma-mass spectrometry (ICP-MS) to screen and discriminate a family of ultratrace but biologically important biomolecules. The feasibility of this novel idea was demonstrated by setting seleno (SeCys) and Se-containing (SeMet) proteins (peptides) as an example. Se-label naturally occurring in the biomolecules acted as an identifier for picking up them out of a large amount of various coexisting proteins (peptides), and CH3Hg-tag that could bind to SeCys rather than SeMet helped discriminating seleno and Se-containing ones simply based on the Se and Hg signals on ICP-MS. This strategy has been applied to screen and discriminate Seleno and Se-containing proteins (peptides) in water-soluble extracts of Se-enriched yeast, and seven selenoproteins (peptides) were detected with both Hg-202 and Se-82 signals out of fifteen Se-containing species using RPLC/ICP-MS, providing valuable information for further identification using a high-resolution structure-selective mass spectrometer. This endogenous element-label plus exogenous element-tag dual-element approach implies that ICP-MS is not only able to quantify targeted proteins (peptides) but also helpful to discover unknown ones during a discovery-based proteomic study.