The human branched chain aminotransferase enzymes are key regulators of glutamate metabolism in the brain and are among a growing number of redox-sensitive proteins. Studies that use thiol-specific reagents and electrospray ionization mass spectrometry demonstrate that the mitochondrial BCAT enzyme has a redox-active CXXC center, which on oxidation forms a disulfide bond (RSSR), via a cysteine sulfenic acid intermediate. Mechanistic details of this redox regulation were revealed by the use of mass spectrometry and dimedone modification. We discovered that the thiol group at position C315 of the CXXC motif acts a redox sensor, whereas the thiol group at position C318 permits reversible regulation by forming an intrasubunit disulphide bond. Because of their roles in redox regulation and catalysis, there is a growing interest in cysteine sulphenic acids. Therefore, development of chemical tags/methods to trap these transient intermediates is of immense importance.
[Show abstract][Hide abstract] ABSTRACT: The ataxia-telangiectasia mutated (ATM) protein kinase is activated by DNA double-strand breaks (DSBs) through the Mre11-Rad50-Nbs1 (MRN) DNA repair complex and orchestrates signaling cascades that initiate the DNA damage response. Cells lacking ATM are also hypersensitive to insults other than DSBs, particularly oxidative stress. We show that oxidation of ATM directly induces ATM activation in the absence of DNA DSBs and the MRN complex. The oxidized form of ATM is a disulfide-cross-linked dimer, and mutation of a critical cysteine residue involved in disulfide bond formation specifically blocked activation through the oxidation pathway. Identification of this pathway explains observations of ATM activation under conditions of oxidative stress and shows that ATM is an important sensor of reactive oxygen species in human cells.
[Show abstract][Hide abstract] ABSTRACT: Protein sulfenic acid formation has long been regarded as unwanted damage caused by reactive oxygen species (ROS). However, over the past 10 years, accumulating evidence has shown that the reversible oxidation of cysteine thiol groups to sulfenic acid functions as a redox-based signal transduction mechanism. Here, we review the mechanisms of sulfenic acid formation by ROS. We present some of the most important roles played by sulfenic acids in living cells as well as the pathways that regulate sulfenic acid formation. We highlight the experimental tools that have been developed to study the cellular sulfenome and show how computational approaches might help to better understand the mechanisms of sulfenic acid formation.
Free Radical Biology and Medicine 07/2011; 51(2):314-26. DOI:10.1016/j.freeradbiomed.2011.04.031 · 5.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Integrated redox proteomics methodologies have contributed in a significant way to provide a better understanding of the oxidative and nitrosative post translational modifications (PTMs) occurring in prokaryotes and eukaryotes during their life cycle or eventually associated with the development of pathological state. On the other hand, a number of irreversible redox PTMs, including nitration, some oxidations, halogenation, and carbonylation, as detected by dedicated redox proteomics approaches, have been associated with specific stressing conditions, highly affecting protein activity and, ultimately, cell functionality. Quantitative redox proteomic approaches were used to identify and quantify redox PTMs in PTPs (Protein tyrosine phosphatases) expressed in human, mouse, and rat cell lines and tissues or in response to stimulation of growth factor receptors. By applying these novel quantitative methods, authors found that normal and malignant cells display distinctive patterns of PTP expression and redox modification.
Chemical Reviews 11/2012; 113(1). DOI:10.1021/cr300073p · 46.57 Impact Factor
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