Chemical Characterization of the Selenoprotein Component of Clostridial Glycine Reductase: Identification of Selenocysteine as the Organoselenium Moiety

A small, heat-stable selenoprotein, one of the components of the glycine reductase complex, was labeled with75Se by growth of Clostridium sticklandii in the presence of Na2 75SeO3. The selenium-containing moiety, which is essential for the biological activity of the protein, was shown to be a seleno...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1976-08, Vol.73 (8), p.2659-2663
Main Authors: Cone, Joyce E., Del Rĩo, Rafael Martĩn, Davis, Joe Nathan, Stadtman, Thressa C.
Format: Article
Language:English
Subjects:
Absorption spectra
Alkylating Agents
Amino Acid Oxidoreductases
Amino acids
Biochemistry
Chromatography
Clostridium - enzymology
Cysteine
Elution
Functional groups
Oxidation
Selenium
Selenoproteins
Spectrophotometry, Ultraviolet
Sulfur
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Summary:A small, heat-stable selenoprotein, one of the components of the glycine reductase complex, was labeled with75Se by growth of Clostridium sticklandii in the presence of Na2 75SeO3. The selenium-containing moiety, which is essential for the biological activity of the protein, was shown to be a selenocysteine residue. It was isolated as its Se-carboxymethyl, Se-carboxyethyl, and Se-aminoethyl derivatives from digests of the pure75Se-labeled protein that had been reduced and treated with the various alkylating agents prior to hydrolysis. In each instance the75Se-labeled moiety obtained from an alkylated protein sample and the corresponding alkyl derivative of authentic selenocysteine were indistinguishable. Several studies of the native selenoprotein detected a chromophore (UVmax238 nm) that appeared upon reduction of the protein with KBH4and rapidly disappeared upon exposure to oxygen. This oxygen-labile chromophore is thought to be the ionized -SeH group of the selenocysteine residue.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.73.8.2659