Subcellular distribution of selenium and Se-containing proteins in human liver

Selenium is an essential trace element in many living organisms. In the pre sent paper, the subcellular distribution of selenium and Se-containing prot eins in human liver samples, which were obtained from normal subjects who h ad an accidental death, was investigated by differential centrifugation and column chromatography. Selenium was mainly enriched in nuclei, mitochondri a and cytosol. Almost half of Se existed in the nuclei due to their large a mount in liver and high Se concentration 15-30% of Se was found in small co mpounds with M-r < 2000 in the liver components separated by dialysis. The average abundance of Se in small molecular mass species of whole-liver was 23.6%, which suggested most of Se associated with biological macromolecules . Eight kinds of Se-containing proteins with molecular mass of 335 +/- 20, 249 +/- 15, 105 +/- 11, 84.6 +/- 5.8, 70.5 +/- 5.4, 45.6 +/- 1.5, 14.8 +/- 2.6, 8.5 +/- 1.2 kDa were found in the subcellular fractions of human liver . Among them the 335, 84.6 and 8.5 kDa proteins were individually present i n one subcellular fraction, whereas the others coexisted in two, three or f our subcellular fractions. The most abundant Se-containing proteins, 70.5 a nd 14.8 kDa, accounted for 33.6% and 48.5% in the whole-liver soluble Se-co ntaining protein, respectively. The former was enriched in cytosol and the latter was mainly present in nuclei and mitochondria. (C) 1999 Elsevier Sci ence B.V. All rights reserved.