Native state fluctuations in a peroxiredoxin active site match motions needed for catalysis

Peroxiredoxins are ubiquitous enzymes that detoxify peroxides and regulate redox signaling. During catal-ysis, a peroxidaticcysteine (C-P) in the conserved active site reduces peroxide while being oxidized to a C-P-sulfenate, prompting a local unfolding event that enables formation of a disulfide with a second, resolving cysteine. Here, we use nuclear magnetic resonance spectroscopy to probe the dynamics of the C-P-thiolate and disulfide forms of Xanthomonas campestris peroxiredoxin Q. Chemical exchange satu-ration transfer behavior of the resting enzyme reveals 26 residues in and around the active site exchanging at a rate of 72 s(-1) with a locally unfolded, high-energy (2.5% of the population) state. This unequivocally es-tablishes that a catalytically relevant local unfolding equilibrium exists in the enzyme's C-P-thiolate form. Also, faster motions imply an active site instability that could promote local unfolding and, based on other work, be exacerbated by C-P-sulfenate formation so as to direct the enzyme along a functional catalytic trajectory.

Automated summary

Peroxiredoxins are enzymes that play important roles in detoxification and redox signaling. Through nuclear magnetic resonance spectroscopy, it has been discovered that Xanthomonas campestris peroxiredoxin Q undergoes local unfolding and dynamics at its active site, which is likely relevant to its catalytic activity.