Selenoproteins and selected protein-bound trace elements in bovine kidney cytosol fraction.

摘要

n 1957 Se was shown to be essential for mammals and birds. It was discovered in 1973 that Se is an integral part of glutathione peroxidase (GSH-Px), an enzyme that metabolizes hydroperoxides and protects cells from oxidative damage. Recent studies have indicated that Se may also serve as an anticarcinogenic agent. A few selenoproteins have been identified in various animal organs but their functions have not yet been established. The role of Se in kidneys is unknown. Kidneys contain the highest level of Se among organs; the majority of this Se is not associated with GSH-Px activity.;A combination of bioanalytical and instrumental neutron activation analysis (INAA) methods has been developed in this work to study selenoproteins and other protein-bound trace elements in the cytosol fraction of bovine kidneys. Differential centrifugation, dialysis, ammonium sulfate precipitation, organic solvent precipitation, assays of enzymatic activities, ion exchange chromatography, gel permeation chromatography, polyacrylamide gel electrophoresis and isoelectric focusing have been applied for separation, purification and characterization of proteins. An INAA method has been developed for the simultaneous multielement determination of total inorganic content in the separated samples. Internal and external quality assessment steps have been followed to ensure the quality of results obtained. The INAA method developed provides very good precision and accuracy.;The existence of three novel Se-containing proteins in the cytosol fraction is reported. These are: (i) Selenoprotein A1 (MW of 71 kDa, pl of 5.5); (ii) Selenoprotein P1 (MW of 62 kDa, pl of 5.4); and (iii) Selenoprotein P2 (MW of 48 kDa, pl of 4.9).;The behavior of 18 elements in bovine kidney cytosol has been examined. Results show