title: Selenium-containing proteins of rat kidney and liver microsomes.
abstract: Selenium (Se)-containing proteins in microsomal fractions of rat kidney and liver were investigated after isotopic labeling of rats with [75Se]selenite. More than 85% of the 75Se in the solubilized microsomal extracts precipitated with protein after trichloroacetic acid treatment. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), used to separate the labeled protein subunits in the solubilized microsomal extracts, revealed several 75Se-containing proteins in addition to glutathione peroxidase. 75Se-labeled subunits with molecular weights of 55, 30, 26, 22, 19, and 17 kDa were present in microsomal fractions of kidney and liver. The 75Se-labeled tryptic peptide of the 55 kDa subunit had the same Rf value on a 17% SDS-PAGE gel as the peptide from plasma selenoprotein P. A time-course study of the labeling of individual protein subunits in kidney and liver microsomes from Se-supplemented and Se-deficient rats showed that most of the 75Se was associated with the 55 kDa subunit 3 hr after injection. The amount of 75Se associated with this protein subunit decreased by 12 hr, with a concurrent increase in the labeling of lower molecular-weight subunits. The results support the hypothesis that there is a mechanism for transfer of Se from the 55 kDa subunit to other Se-containing proteins.
authors.affiliation: Department of Food Science and Technology, University of California, Davis 95616.
authors.forename: A J
authors.initials: AJ
authors.lastname: Viljoen
authors.forename: P A
authors.initials: PA
authors.lastname: Motchnik
authors.forename: A L
authors.initials: AL
authors.lastname: Tappel
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D005979:Glutathione Peroxidase / Q000032:analysis; D007668:Kidney / Q000032:analysis* / Q000378:metabolism / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000032:analysis* / Q000378:metabolism; D008862:Microsomes, Liver / Q000032:analysis* / Q000378:metabolism; D008970:Molecular Weight; D011506:Proteins / Q000032:analysis* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D020887:Selenious Acid; D012643:Selenium / Q000032:analysis* / Q000378:metabolism; D012644:Selenium Radioisotopes
chemical_list: D001798:Blood Proteins; D011506:Proteins; D012644:Selenium Radioisotopes; D005979:Glutathione Peroxidase; D020887:Selenious Acid; D012643:Selenium