Deletion of the carboxyl terminal of thioredoxin reductase C of Arabidopsis facilitates oligomerization

Abstract

The hydrophobicity of NADPH-thioredoxin reductase C (AtNTRC) of Arabidopsis was determined at the carboxyl terminal based on a Kyte-Dolittle hydropathy plot. A carboxyl-terminal deletion mutant of AtNTRC was made in this study to determine whether such deletion could affect the structure and function of AtNTRC. The mutant protein with 14 amino acids deleted at the carboxyl terminus (designated as AtNTRCΔC14) was purified. It was found that AtNTRCΔC14 protein had higher hydrophobicity compared to AtNTRC. Such increase in hydrophobicity of AtNTRCΔC14 affected its native structure and functions. In addition, AtNTRCΔC14 had higher number of high oligomeric complexes compared to AtNTRC based on native-gel electrophoresis and size exclusion chromatography. Although the chaperone activity of AtNTRCΔC14 was enhanced, its NADPH-dependent reductase activity was lower compared to AtNTRC. Therefore, the hydrophobicity of the thioredoxin domain of AtNTRC is important for forming high molecular weight complexes and for maintaining functional balance between chaperone activity and thioredoxin reductase activity.