Acetylation Regulates Thioredoxin Reductase Oligomerization and Activity.

Thioredoxin reductase 1 (TrxR1) is a cancer target and essential selenoprotein that defends the cell against reactive oxygen species and regulates cellular signaling and redox pathways. Previous cell-based studies correlated TrxR1 acetylation with modulated cellular reduction activity, yet the function of specific acetylation sites on TrxR1 remains unknown. We produced site-specifically acetylated TrxR1 variants that also contain selenocysteine (Sec). We demonstrated efficient high-fidelity protein synthesis with 22 different amino acids by simultaneous UAG codon reassignment to Nɛ-acetyl-lysine and UGA codon recoding to Sec. We characterized TrxR1 variants acetylated at physiologically relevant sites and found that single acetylation sites increased TrxR1 activity, enhancing the apparent catalytic rate up to 2.7-fold. The activity increase in acetylated TrxR1 (acTrxR1) is reversible and is reduced following deacetylation with histone deacetylase. Here we present a novel mechanism through which acetylation increases TrxR1 activity by destabilizing low-activity TrxR1 multimers, increasing the population of active dimeric TrxR1. Antioxid. Redox Signal. 29, 377-388.