Nβ domain contributes to NaTrxh stability. N- and C-termini are not involved in its reductase activity. (A) SDS-PAGE analysis of different NaTrxh versions fused to GST expressed in E. coli cells. Upper panels: Coomassie blue stained gel; lower panels: western-blot immuno-stained with anti-NaTrxh antibody. S: soluble fraction; I: insoluble fraction; GST: gluthathione S-transferase; NaT: full-length NaTrxh; NaTΔα: NaTrxhΔNα mutant; NaTΔβ: NaTrxhΔNβ; NaTΔαβ: NaTrxhΔNαβ; NaTΔCOO: NaTrxhΔCOO. Arrows indicate the signal corresponding to the different NaTrxh:GST versions. (B) Thioredoxin activity assay using insulin as substrate and DTT as electron donor (Holmgren, 1979). Circles: NaTrxh; Diamonds: NaTrxhΔNα; Squares: NaTrxhΔNαβ; Triangles: NaTrxhΔCOO; Crosses: only DTT.