Selenocysteine-containing thioredoxin reductase in C. elegans
V N Gladyshev1, M Krause, X M Xu
1Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588, USA. vng@unlinfo2.unl.edu
Biochemical and Biophysical Research Communications
|June 11, 1999
Summary
The nematode Caenorhabditis elegans possesses two thioredoxin reductase homologs. One, TR-Se, is a selenoprotein and the major selenoprotein in C. elegans, highlighting selenium
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Mammalian thioredoxin reductases feature a C-terminal selenocysteine (Sec) residue encoded by TGA.
- These mammalian enzymes exhibit limited homology with bacterial, yeast, and plant counterparts.
- C. elegans possesses two thioredoxin reductase homologs, differing in their Sec incorporation mechanisms.
Purpose of the Study:
- To investigate the thioredoxin reductase family in Caenorhabditis elegans.
- To characterize a novel selenoprotein, TR-Se, in C. elegans.
- To elucidate the role of selenium in the C. elegans thioredoxin system.
Main Methods:
- Sequence homology analysis comparing C. elegans and mammalian thioredoxin reductases.
- Biochemical characterization of TR-Se using 75Se labeling, affinity chromatography, and gel electrophoresis.
- Heterologous expression of TR-Se in E. coli with a bacterial SECIS element.
Main Results:
- Identified two C. elegans thioredoxin reductase homologs: TR-S (using cysteine) and TR-Se (using selenocysteine).
- TR-Se lacks a canonical Sec insertion sequence (SECIS) element but was confirmed as a selenoprotein.
- TR-Se demonstrated significant sequence similarity to mammalian TR1 and TR2, and was identified as the major selenoprotein in C. elegans.
Conclusions:
- TR-Se is the predominant naturally occurring selenoprotein in C. elegans.
- The thioredoxin system and selenium play a crucial role in C. elegans.
- The mechanism of Sec incorporation in TR-Se, despite lacking a canonical SECIS element, warrants further investigation.
