Mechanism of Redox-mediated Guanine Nucleotide Exchange on Redox-active Rho GTPases

Jongyun Heo,Sharon L Campbell

doi:10.1074/jbc.m504768200

Jongyun Heo, Sharon L Campbell

Open Access

https://doi.org/10.1074/jbc.m504768200

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Abstract

Rho GTPases regulate multiple cellular processes including actin cytoskeletal rearrangements, transcriptional regulation, and oxidant production. The studies described herein demonstrate that small molecule redox agents, in addition to protein regulatory factors, can regulate the activity of redox-active Rho GTPases. A novel (GXXXXGK(S/T)C) motif, conserved in a number of Rho GTPases, appears critical for redox-mediated guanine nucleotide dissociation in vitro. A detailed molecular mechanism for redox regulation of GXXXXGK(S/T)C motif-containing Rho GTPases is proposed.

Highlights

Rho GTPases comprise a large branch of the Ras superfamily of small guanine nucleotide-binding proteins and include the well characterized family members Rac1, RhoA, and Cdc42 [1]
We have previously proposed a mechanism whereby reaction of either nitric oxide (NO)/O2 or O2. with Ras generates a Cys118-thiyl radical (Cys1181⁄7), which in turn promotes formation of a guanine radical intermediate resulting in perturbation of Ras guanine nucleotide interactions and accelerated release of GDP as GDP derivatives from Ras [11, 12]
We show that H2O2 alone does not facilitate Rho GTPase guanine nucleotide dissociation, whereas H2O2 in the presence of a transition metal (H2O2/Cu2ϩ) causes production of OH1⁄7 [24], which may facilitate guanine nucleotide dissociation from

Summary

Introduction

Rho GTPases comprise a large branch of the Ras superfamily of small guanine nucleotide-binding proteins and include the well characterized family members Rac1, RhoA, and Cdc42 [1]. If the mechanism of redox-mediated guanine nucleotide dissociation of GXXXXGK(S/T)C motif-containing Rho GTPases (see below) is similar to that of Ras GTPases [11, 12], electronic coupling between the Rac1 Cys18-thiyl radical (Cys181⁄7) and the Phe28 side chain is expected, with the Phe28 side chain serving as an electron conduit between the Rac1 Cys181⁄7 and the bound

Results

Conclusion