Single-molecule studies of disulfide bond reduction pathways used by human thioredoxin

Abstract

How to cite this manuscriptIf you make reference to this version of the manuscript, use the following information: Szoszkiewicz, R. (2013). Single-molecule studies of disulfide bond reduction pathways used by human thioredoxin. Retrieved from http://krex.ksu.edu Published Version InformationCitation: Szoszkiewicz, R. (2013 8 molecules are stretched at constant force applied by a cantilever in a force-clamp mode of atomic force microscopy (FC-AFM). Disulfide reduction events are accurately detected from stepwise increases in the end-to-end length of (I27 SS ) 8 . Earlier FC-AFM studies observed one disulfide reduction pathway used by hTrx and suggested an additional electron tunnelling mechanism. Here, a very large set of unbiased FC-AFM data is collected in a range of clamping forces. By analyzing the data using exponential fits and dwell times histograms two disulfide reduction pathways used by hTrx are resolved. Based on previous studies one of these pathways is attributed to force-dependent Michaelis-Menten catalysis. The latter reduction pathway is weakly forceinhibited and occurs sporadically. Bimolecular nucleophilic substitutions (S N 2) and electron tunnelling (ET) mechanisms are discussed to explain the second pathway. Direct S N 2 and ET mechanisms cannot be discounted, but a hypothetical E2-S N 2 mechanism involving a hydride reducing a disulfide bond provides an interesting alternative, which needs to be verified in future experiments.

Unexpected mechanochemical complexity in the mechanistic scenarios of disulfide bond reduction in alkaline solution

“…Disulfide bond reduction is one of the most studied classes of reactions in the context of covalent mechanochemistry. [1][2][3][4][5] Following the pioneering forceclamp AFM study of the thiolate/disulfide exchange reaction 6 , the effect of tensile forces on the kinetics and reaction mechanisms of disulfide bond reductions has been intensively investigated by means of single-molecule force spectroscopy, [7][8][9][10][11][12][13][14][15] molecular force probes 16,17 and computational studies. [18][19][20][21][22][23][24][25][26] All the efforts undertaken to decipher the intricacies of the coupling of mechanical stress and disulfide reactivity are not only very important from a fundamental science point of view, but also for biochemistry and polymer-based materials science and technology.…”