Exploring the conformational transition between the fully folded and locally unfolded substates of Escherichia coli thiol peroxidase

摘要: Thiol peroxidase from Escherichia coli (EcTPx) is a peroxiredoxin that catalyzes the reduction of different hydroperoxides. During catalytic cycle EcTPx, peroxidatic cysteine (CP) oxidized to sulfenic acid by peroxide, then resolving (CR) condenses with CP form disulfide bond, which finally reduced thioredoxin. Purified EcTPx as dithiol and behaves monomer under near physiological conditions. Although secondary structure rearrangements are present when comparing redox states enzyme, no significant differences in unfolding free energies observed reducing oxidizing A conformational change denominated fully folded (FF) locally unfolded (LU) transition, involving partial αH2 αH3, must occur enable formation bond since cysteines 12 apart FF conformation EcTPx. To explore this process, → LU transitions were studied using conventional molecular dynamics simulations an enhanced sampling technique for oxidation protonation active site residues CR. Our results suggest transition has higher associated energy barrier than refolding process agreement relatively low experimental turnover number Furthermore, silico designed single-point mutants αH3 events, suggesting native interactions not evolutionarily optimized speed-up wild-type