Reactivity of disulfide bonds is markedly affected by structure and environment: implications for protein modification and stability.

Anna K Croft,Carl H Schiesser,David I Pattison,Michael J Davies,Maryam Karimi,Leo Radom,Bun Chan,Marta T Ignasiak

doi:10.1038/srep38572

Abstract

Disulfide bonds play a key role in stabilizing protein structures, with disruption strongly associated with loss of protein function and activity. Previous data have suggested that disulfides show only modest reactivity with oxidants. In the current study, we report kinetic data indicating that selected disulfides react extremely rapidly, with a variation of 104 in rate constants. Five-membered ring disulfides are particularly reactive compared with acyclic (linear) disulfides or six-membered rings. Particular disulfides in proteins also show enhanced reactivity. This variation occurs with multiple oxidants and is shown to arise from favorable electrostatic stabilization of the incipient positive charge on the sulfur reaction center by remote groups, or by the neighboring sulfur for conformations in which the orbitals are suitably aligned. Controlling these factors should allow the design of efficient scavengers and high-stability proteins. These data are consistent with selective oxidative damage to particular disulfides, including those in some proteins.

Highlights

Monocytes and macrophages results in the assembly and activation of complexes that generate oxidants, including NADPH oxidases (NOXs) that generates superoxide radicals (O2−·) and H2O2 by dismutation, and nitric oxide synthases that produce nitric oxide (NO·)[10,11]
Radical-mediated damage to biological targets has been studied extensively, but less is known about the reactions of hypochlorous acid (HOCl), hypobromous acid (HOBr), HOSCN, ONOOH and 1O212,14–16
In the present study we show that the apparent second-order rate constants (k2) for oxidation of disulfide bonds vary by up to 104-fold, and with multiple oxidants, with the variations arising from interactions between the reaction center and nearby heteroatoms

Summary

Introduction

Monocytes and macrophages results in the assembly and activation of complexes that generate oxidants, including NADPH oxidases (NOXs) that generates superoxide radicals (O2−·) and H2O2 by dismutation, and nitric oxide synthases that produce nitric oxide (NO·)[10,11]. Stimulated neutrophils, monocytes and some tissue macrophages release myeloperoxidase that utilises H2O2 to generate powerful two-electron oxidants [e.g. hypochlorous acid (HOCl), hypobromous acid (HOBr), hypothiocyanous acid (HOSCN)] and radicals[13,14]. These processes are critical to efficient pathogen killing, but result in significant collateral damage to host tissues[15]. Proteins are major targets for these oxidants as a result of their abundance, and high rate constants for reaction, with sulfur-containing amino acids being prone to modification due to the presence of the reactive sulfur center (reviewed)[15,17,18]. Theoretical computations have been used to help rationalize the experimental observations

Methods

Results

Conclusion