Selenophosphate synthetase 2 is essential for selenoprotein biosynthesis

Authors

Xue-Ming Xu, National Cancer Institute, National Institutes of Health, Bethesda, MDFollow
Bradley A. Carlson, National Cancer Institute, National Institutes of Health, Bethesda, MDFollow
Robert Irons, National Cancer Institute, National Institutes of Health, Bethesda, MD
Heiko Mix, University of Nebraska-Lincoln
Nianxin Zhong, National Cancer Institute, National Institutes of Health, Bethesda, MD
Vadim Gladyshev, University of Nebraska-LincolnFollow
Dolph L. Hatfield, National Cancer Institute, National Institutes of Health, Bethesda, MDFollow

Date of this Version

April 2007

Comments

Published in Biochem. J. (2007) 404, 115–120 (Printed in Great Britain). ©The Authors Journal compilation ©2007 Biochemical Society. Permission to use. http://www.biochemj.org

Abstract

Selenophosphate synthetase (SelD) generates the selenium donor for selenocysteine biosynthesis in eubacteria. One homologue of SelD in eukaryotes is SPS1 (selenophosphate synthetase 1) and a second one, SPS2, was identified as a selenoprotein in mammals. Earlier in vitro studies showed SPS2, but not SPS1, synthesized selenophosphate from selenide, whereas SPS1 may utilize a different substrate. The roles of these enzymes in selenoprotein synthesis in vivo remain unknown. To address their function in vivo, we knocked down SPS2 in NIH3T3 cells using small interfering RNA and found that selenoprotein biosynthesis was severely impaired, whereas knockdown of SPS1 had no effect. Transfection of SPS2 into SPS2 knockdown cells restored selenoprotein biosynthesis, but SPS1 did not, indicating that SPS1 cannot complement SPS2 function. These in vivo studies indicate that SPS2 is essential for generating the selenium donor for selenocysteine biosynthesis in mammals, whereas SPS1 probably has a more specialized, non-essential role in selenoprotein metabolism.