Equimolar Hg-Se complex binds to selenoprotein P

Area of Science:

• Biochemistry
• Toxicology
• Analytical Chemistry

Background:

• Mercury (Hg) is a toxic heavy metal, and selenium (Se) is known to bind Hg.
• Plasma proteins play a role in the transport and detoxification of metals.
• Selenoprotein P (Sel P) is a major selenium-containing protein in plasma.

Purpose of the Study:

• To investigate the in vitro binding of equimolar mercury and selenium to a specific plasma protein.
• To elucidate the mechanism of mercury detoxification involving selenium and plasma proteins.

Main Methods:

• High-Performance Liquid Chromatography/Inductively Coupled Argon Plasma-Mass Spectrometry (HPLC/ICP-MS) with enriched stable isotopes.
• Incubation of rat serum with HgCl2 and 82Se-enriched selenite in the presence of glutathione.
• Size exclusion chromatography to separate and analyze protein complexes.

Main Results:

• Equimolar mercury and selenium co-eluted with endogenous selenium on a size exclusion column.
• The endogenous 78Se peak, identified as selenoprotein P (Sel P), showed affinity to heparin.
• The 82Se/endogenous Se ratio indicated that over 1,000 units of (Hg-Se) bind to Sel P, forming a {(Hg-Se)n}m-Sel P complex.

Conclusions:

• Equimolar mercury and selenium bind to selenoprotein P (Sel P) in plasma.
• This binding forms a stable complex, suggesting a detoxification pathway for mercury.
• The study provides insights into the molecular interactions of mercury, selenium, and Sel P.