Selenocysteine-containing proteins from rat and monkey plasma

Area of Science:

• Biochemistry
• Trace Element Metabolism
• Animal Physiology

Background:

• Selenium is an essential trace element crucial for various biological functions.
• Understanding selenium transport mechanisms is vital for comprehending its metabolism and bioavailability.
• Plasma proteins are often involved in the transport of essential nutrients and metabolites.

Purpose of the Study:

• To investigate the potential role of a specific selenium-containing plasma protein in selenium transport.
• To characterize the properties of this protein in rat and monkey plasma.

Main Methods:

• Radioactive selenium isotopes ([75Se]selenite and [75Se]selenomethionine) were used to label plasma proteins.
• Gel filtration chromatography was employed to determine the native molecular weight of the protein.
• Sodium dodecyl sulfate (SDS) gel filtration was used to determine the molecular weight of a selenium-containing polypeptide derived from the protein.

Main Results:

• A selenium-binding protein with a native molecular weight of approximately 80,000 was identified in both rat and monkey plasma.
• A selenium-containing polypeptide fragment of this protein had a molecular weight of about 45,000.
• Selenium was found to be incorporated as selenocysteine within the protein.
• In rats, less than 5% of plasma selenium was normally bound to this protein, with a short selenium half-life (a few hours).

Conclusions:

• The characterized plasma protein exhibits properties consistent with a role in selenium transport.
• The findings suggest this protein may facilitate the movement of selenium within the bloodstream.
• Further research is warranted to fully elucidate the physiological significance of this selenium-binding protein.