Speciation of selenoproteins in Se-contaminated wildlife by gel electrophoresis and laser ablation-ICP-MS

Selenium (Se) is a trace element of both health and environmental concerns due to its nutritional requirement and teratogenic effect on wildlife inhabiting Se-contaminated aquatic systems. It is now understood that the key to Se nutrition lies in the biochemistry of selenoproteins including glutathione peroxidase, thioredoxin reductase, and those yet to be defined. However, it is still unclear regarding the molecular mechanism(s) underlying Se toxicity on embryogenesis of sensitive aquatic bird and fish species. It is possible that Se incorporation into proteins may also play an important role in Se toxicity since Se is enriched in total proteins of aquatic predators. Selenoprotein speciation has been a challenge due to the labile and trace nature of the seleno amino acid components. This report demonstrates that the difficulty can be overcome by the combination of denaturing gel electrophoresis and ultrasensitive laser ablation (LA)-ICP-MS. A selenoprotein standard was analyzed to illustrate the semi-quantitative aspect of this analysis. Protein extracts of an avocet embryo and a largemouth bass ovary collected from Se-laden waters were also examined and revealed 8 and 5 distinct bands of Se-containing proteins, respectively. Quantitative Se analysis of these proteins using LA-ICP-MS appears to be feasible but awaits further development.