Nitration-driven structural changes in Hsp90 linked to gain of pathological functions.

Protein tyrosine (Y) nitration is an oxidative modification that occurs in pathological conditions such as neurodegenerative diseases and solid tumors. Depending on the location of the tyrosine residue, nitration can modify protein structure and function and affect cellular processes. We previously showed that site-specific nitration of the molecular chaperone heat shock protein 90 (Hsp90) leads to distinct pathological gain-of-function that cannot be compensated or overcome by native Hsp90.

Hydrogen peroxide transport by aquaporins: insights from molecular modeling and simulations.

Hydrogen peroxide (HO) is a key reactive oxygen species involved in cellular redox signaling and oxidative stress. Due to its polar nature, its transport across membranes is regulated by aquaporins (AQPs), membrane channels traditionally known for HO transport. Certain AQPs, known as peroxiporins, facilitate selective HO permeation, playing critical roles in mantaining redox homeostasis.

Human glutathione transferases catalyze the reaction between glutathione and nitrooleic acid.

Nitroalkene fatty acids (NO-FAs) are formed endogenously. They regulate cell signaling pathways and are being developed clinically to treat inflammatory diseases. NO-FAs are electrophilic and form thioether adducts with glutathione (GSH), which are exported from cells.

A Noncatalytic Cysteine Residue Modulates Cobalamin Reactivity in the Human B Processing Enzyme CblC.

Human CblC catalyzes the indispensable processing of dietary vitamin B by the removal of its β-axial ligand and an either one- or two-electron reduction of its cobalt center to yield cob(II)alamin and cob(I)alamin, respectively. Human CblC possesses five cysteine residues of an unknown function. We hypothesized that Cys149, conserved in mammals, tunes the CblC reactivity.

Mg binding to coenzyme A.

Magnesium (Mg), the second most abundant intracellular cation, plays a crucial role in cellular functions. In this study, we investigate the interaction between Mg and coenzyme A (CoA), a thiol-containing cofactor central to cellular metabolism also involved in protein modifications. Isothermal titration calorimetry revealed a 1:1 binding stoichiometry between Mg and free CoA under biologically relevant conditions.

Permeation mechanisms of hydrogen peroxide and water through Plasma Membrane Intrinsic Protein aquaporins.

Hydrogen peroxide (H2O2) transport by aquaporins (AQP) is a critical feature for cellular redox signaling. However, the H2O2 permeation mechanism through these channels remains poorly understood. Through functional assays, two Plasma membrane Intrinsic Protein (PIP) AQP from Medicago truncatula, MtPIP2;2 and MtPIP2;3 have been identified as pH-gated channels capable of facilitating the permeation of both water (H2O) and H2O2.

Catalytic Mechanism of Methionine Sulfoxide Reductase A.

The oxidation of Met to methionine sulfoxide (MetSO) by oxidants such as hydrogen peroxide, hypochlorite, or peroxynitrite has profound effects on protein function. This modification can be reversed by methionine sulfoxide reductases (msr). In the context of pathogen infection, the reduction of oxidized proteins gains significance due to microbial oxidative damage generated by the immune system.

Kinetic and structural assessment of the reduction of human 2-Cys peroxiredoxins by thioredoxins.

We have studied the reduction reactions of two cytosolic human peroxiredoxins (Prx) in their disulfide form by three thioredoxins (Trx; two human and one bacterial), with the aim of better understanding the rate and mechanism of those reactions, and their relevance in the context of the catalytic cycle of Prx. We have developed a new methodology based on stopped-flow and intrinsic fluorescence to study the bimolecular reactions, and found rate constants in the range of 10 -10  m  s in all cases, showing that there is no marked kinetic preference for the expected Trx partner. By combining experimental findings and molecular dynamics studies, we found that the reactivity of the nucleophilic cysteine (C ) in the Trx is greatly affected by the formation of the Prx-Trx complex.

Minimum Free Energy Pathways of Reactive Processes with Nudged Elastic Bands.

The determination of minimum free energy pathways (MFEP) is one of the most widely used strategies to study reactive processes. For chemical reactions in complex environments, the combination of quantum mechanics (QM) with a molecular mechanics (MM) representation is usually necessary in a hybrid QM/MM framework. However, even within the QM/MM approximation, the affordable sampling of the phase space is, in general, quite restricted.

Mitochondrial Peroxiredoxin 3 Is Rapidly Oxidized and Hyperoxidized by Fatty Acid Hydroperoxides.

Human peroxiredoxin 3 (Prx3) is a thiol-based peroxidase responsible for the reduction of most hydrogen peroxide and peroxynitrite formed in mitochondria. Mitochondrial disfunction can lead to membrane lipoperoxidation, resulting in the formation of lipid-bound fatty acid hydroperoxides (FA-OOHs) which can be released to become free fatty acid hydroperoxides (FA-OOHs). Herein, we report that Prx3 is oxidized and hyperoxidized by FA-OOHs including those derived from arachidonic acid and eicosapentaenoic acid peroxidation at position 15 with remarkably high rate constants of oxidation (>3.

Redox sensitive human mitochondrial aconitase and its interaction with frataxin: In vitro and in silico studies confirm that it takes two to tango.

Mitochondrial aconitase (ACO2) has been postulated as a redox sensor in the tricarboxylic acid cycle. Its high sensitivity towards reactive oxygen and nitrogen species is due to its particularly labile [4Fe-4S] prosthetic group which yields an inactive [3Fe-4S] cluster upon oxidation. Moreover, ACO2 was found as a main oxidant target during aging and in pathologies where mitochondrial dysfunction is implied.

Novel Lennard-Jones Parameters for Cysteine and Selenocysteine in the AMBER Force Field.

Cysteine is a common amino acid with a thiol group that plays a pivotal role in a variety of scenarios in redox biochemistry. In contrast, selenocysteine, the 21st amino acid, is only present in 25 human proteins. Classical force-field parameters for cysteine and selenocysteine are still scarce.

De novo sequencing and construction of a unique antibody for the recognition of alternative conformations of cytochrome in cells.

Cytochrome (cyt ) can undergo reversible conformational changes under biologically relevant conditions. Revealing these alternative cyt conformers at the cell and tissue level is challenging. A monoclonal antibody (mAb) identifying a key conformational change in cyt was previously reported, but the hybridoma was rendered nonviable.

Crystal structure of Trypanosoma cruzi heme peroxidase and characterization of its substrate specificity and compound I intermediate.

The protozoan parasite Trypanosoma cruzi is the causative agent of American trypanosomiasis, otherwise known as Chagas disease. To survive in the host, the T. cruzi parasite needs antioxidant defense systems.

The superoxide radical switch in the biology of nitric oxide and peroxynitrite.

The free radical nitric oxide (NO) is a key mediator in different physiological processes such as vasodilation, neurotransmission, inflammation, and cellular immune responses, and thus preserving its bioavailability is essential. In several disease conditions, superoxide radical (O) production increases and leads to the rapid "inactivation" of NO by a diffusion-controlled radical termination reaction that yields a potent and short-lived oxidant, peroxynitrite. This reaction not only limits NO bioavailability for physiological signal transduction but also can divert and switch the biochemistry of NO toward nitrooxidative processes.

Thiol-based chemical probes exhibit antiviral activity against SARS-CoV-2 via allosteric disulfide disruption in the spike glycoprotein.

The development of small-molecules targeting different components of SARS-CoV-2 is a key strategy to complement antibody-based treatments and vaccination campaigns in managing the COVID-19 pandemic. Here, we show that two thiol-based chemical probes that act as reducing agents, P2119 and P2165, inhibit infection by human coronaviruses, including SARS-CoV-2, and decrease the binding of spike glycoprotein to its receptor, the angiotensin-converting enzyme 2 (ACE2). Proteomics and reactive cysteine profiling link the antiviral activity to the reduction of key disulfides, specifically by disruption of the Cys379-Cys432 and Cys391-Cys525 pairs distal to the receptor binding motif in the receptor binding domain (RBD) of the spike glycoprotein.

PIP aquaporin pH-sensing is regulated by the length and charge of the C-terminal region.

Plant PIP aquaporins play a central role in controlling plant water status. The current structural model for PIP pH-gating states that the main pH sensor is located in loopD and that all the mobile cytosolic elements participate in a complex interaction network that ensures the closed structure. However, the precise participation of the last part of the C-terminal domain (CT) in PIP pH gating remains unknown.

Cardiolipin interactions with cytochrome c increase tyrosine nitration yields and site-specificity.

The interaction between cytochrome c and cardiolipin is a relevant process in the mitochondrial redox homeostasis, playing roles in the mechanism of electron transfer to cytochrome c oxidase and also modulating cytochrome c conformation, reactivity and function. Peroxynitrite is a widespread nitrating agent formed in mitochondria under oxidative stress conditions, and can result in the formation of tyrosine nitrated cytochrome c. Some of the nitro-cytochrome c species undergo conformational changes at physiological pH and increase its peroxidase activity.

Akt Is S-Palmitoylated: A New Layer of Regulation for Akt.

The protein kinase Akt/PKB participates in a great variety of processes, including translation, cell proliferation and survival, as well as malignant transformation and viral infection. In the last few years, novel Akt posttranslational modifications have been found. However, how these modification patterns affect Akt subcellular localization, target specificity and, in general, function is not thoroughly understood.

Genetic and transcriptomic evidences suggest ARO10 genes are involved in benzenoid biosynthesis by yeast.

Benzenoids are compounds associated with floral and fruity flavours in flowers, fruits and leaves and present a role in hormonal signalling in plants. These molecules are produced by the phenyl ammonia lyase pathway. However, some yeasts can also synthesize them from aromatic amino acids using an alternative pathway that remains unknown.

Exploring the conformational transition between the fully folded and locally unfolded substates of Escherichia coli thiol peroxidase.

Thiol peroxidase from Escherichia coli (EcTPx) is a peroxiredoxin that catalyzes the reduction of different hydroperoxides. During the catalytic cycle of EcTPx, the peroxidatic cysteine (C) is oxidized to a sulfenic acid by peroxide, then the resolving cysteine (C) condenses with the sulfenic acid of C to form a disulfide bond, which is finally reduced by thioredoxin. Purified EcTPx as dithiol and disulfide behaves as a monomer under near physiological conditions.