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Rocha RF, Martins PGA, D'Muniz Pereira H, Brandão-Neto J, Thiemann OH, Terenzi H, Menegatti ACO. Crystal structure of the Cys-NO modified YopH tyrosine phosphatase. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140754. [PMID: 34995802 DOI: 10.1016/j.bbapap.2022.140754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 12/21/2021] [Accepted: 01/01/2022] [Indexed: 06/14/2023]
Abstract
Protein tyrosine phosphatases (PTPs) are key virulence factors in pathogenic bacteria, consequently, they have become important targets for new approaches against these pathogens, especially in the fight against antibiotic resistance. Among these targets of interest YopH (Yersinia outer protein H) from virulent species of Yersinia is an example. PTPs can be reversibly inhibited by nitric oxide (NO) since the oxidative modification of cysteine residues may influence the protein structure and catalytic activity. We therefore investigated the effects of NO on the structure and enzymatic activity of Yersinia enterocolitica YopH in vitro. Through phosphatase activity assays, we observe that in the presence of NO YopH activity was inhibited by 50%, and that this oxidative modification is partially reversible in the presence of DTT. Furthermore, YopH S-nitrosylation was clearly confirmed by a biotin switch assay, high resolution mass spectrometry (MS) and X-ray crystallography approaches. The crystal structure confirmed the S-nitrosylation of the catalytic cysteine residue, Cys403, while the MS data provide evidence that Cys221 and Cys234 might also be modified by NO. Interestingly, circular dichroism spectroscopy shows that the S-nitrosylation affects secondary structure of wild type YopH, though to a lesser extent on the catalytic cysteine to serine YopH mutant. The data obtained demonstrate that S-nitrosylation inhibits the catalytic activity of YopH, with effects beyond the catalytic cysteine. These findings are helpful for designing effective YopH inhibitors and potential therapeutic strategies to fight this pathogen or others that use similar mechanisms to interfere in the signal transduction pathways of their hosts.
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Affiliation(s)
- Ruth F Rocha
- Laboratório de Biologia Molecular Estrutural, Departamento de Bioquímica, CCB, Universidade Federal de Santa Catarina, Florianópolis 88040-900, Brazil
| | - Priscila G A Martins
- Laboratório de Biologia Molecular Estrutural, Departamento de Bioquímica, CCB, Universidade Federal de Santa Catarina, Florianópolis 88040-900, Brazil
| | | | - José Brandão-Neto
- Diamond Light Source, Diamond House, Harwell Science and Innovation Campus, Didcot OX110DE, United Kingdom
| | - Otavio Henrique Thiemann
- São Carlos Institute of Physics, University of São Paulo, São Carlos, Brazil; Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, Brazil
| | - Hernán Terenzi
- Laboratório de Biologia Molecular Estrutural, Departamento de Bioquímica, CCB, Universidade Federal de Santa Catarina, Florianópolis 88040-900, Brazil.
| | - Angela C O Menegatti
- Department of Molecular Biology, Federal University of Paraiba, João Pessoa 58051-900, Brazil.
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Recent Updates on Development of Protein-Tyrosine Phosphatase 1B Inhibitors for Treatment of Diabetes, Obesity and Related Disorders. Bioorg Chem 2022; 121:105626. [DOI: 10.1016/j.bioorg.2022.105626] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 12/19/2021] [Accepted: 01/13/2022] [Indexed: 01/30/2023]
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3
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Nitric oxide loading reduces sickle red cell adhesion and vaso-occlusion in vivo. Blood Adv 2020; 3:2586-2597. [PMID: 31484636 DOI: 10.1182/bloodadvances.2019031633] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 07/23/2019] [Indexed: 12/29/2022] Open
Abstract
Sickle red blood cells (SSRBCs) are adherent to the endothelium, activate leukocyte adhesion, and are deficient in bioactive nitric oxide (NO) adducts such as S-nitrosothiols (SNOs), with reduced ability to induce vasodilation in response to hypoxia. All these pathophysiologic characteristics promote vascular occlusion, the hallmark of sickle cell disease (SCD). Loading hypoxic SSRBCs in vitro with NO followed by reoxygenation significantly decreased epinephrine-activated SSRBC adhesion to the endothelium, the ability of activated SSRBCs to mediate leukocyte adhesion in vitro, and vessel obstruction in vivo. Because transfusion is frequently used in SCD, we also determined the effects of banked (SNO-depleted) red blood cells (RBCs) on vaso-occlusion in vivo. Fresh or 14-day-old normal RBCs (AARBCs) reduced epinephrine-activated SSRBC adhesion to the vascular endothelium and prevented vaso-occlusion. In contrast, AARBCs stored for 30 days failed to decrease activated SSRBC adhesivity or vaso-occlusion, unless these RBCs were loaded with NO. Furthermore, NO loading of SSRBCs increased S-nitrosohemoglobin and modulated epinephrine's effect by upregulating phosphorylation of membrane proteins, including pyruvate kinase, E3 ubiquitin ligase, and the cytoskeletal protein 4.1. Thus, abnormal SSRBC NO/SNO content both contributes to the vaso-occlusive pathophysiology of SCD, potentially by affecting at least protein phosphorylation, and is potentially amenable to correction by (S)NO repletion or by RBC transfusion.
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Ruddraraju KV, Zhang ZY. Covalent inhibition of protein tyrosine phosphatases. MOLECULAR BIOSYSTEMS 2018; 13:1257-1279. [PMID: 28534914 DOI: 10.1039/c7mb00151g] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Protein tyrosine phosphatases (PTPs) are a large family of 107 signaling enzymes that catalyze the hydrolytic removal of phosphate groups from tyrosine residues in a target protein. The phosphorylation status of tyrosine residues on proteins serve as a ubiquitous mechanism for cellular signal transduction. Aberrant function of PTPs can lead to many human diseases, such as diabetes, obesity, cancer, and autoimmune diseases. As the number of disease relevant PTPs increases, there is urgency in developing highly potent inhibitors that are selective towards specific PTPs. Most current efforts have been devoted to the development of active site-directed and reversible inhibitors for PTPs. This review summarizes recent progress made in the field of covalent inhibitors to target PTPs. Here, we discuss the in vivo and in vitro inactivation of various PTPs by small molecule-containing electrophiles, such as Michael acceptors, α-halo ketones, epoxides, and isothiocyanates, etc. as well as oxidizing agents. We also suggest potential strategies to transform these electrophiles into isozyme selective covalent PTP inhibitors.
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Affiliation(s)
- Kasi Viswanatharaju Ruddraraju
- Department of Medicinal Chemistry and Molecular Pharmacology, Department of Chemistry, Center for Cancer Research, and Institute for Drug Discovery, Purdue University, 720 Clinic Drive, West Lafayette, IN 47907, USA.
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Heneberg P. Reactive nitrogen species and hydrogen sulfide as regulators of protein tyrosine phosphatase activity. Antioxid Redox Signal 2014; 20:2191-209. [PMID: 24328688 PMCID: PMC3994915 DOI: 10.1089/ars.2013.5493] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
SIGNIFICANCE Redox modifications of thiols serve as a molecular code enabling precise and complex regulation of protein tyrosine phosphatases (PTPs) and other proteins. Particular gasotransmitters and even the redox modifications themselves affect each other, of which a typical example is S-nitrosylation-mediated protection against the further oxidation of protein thiols. RECENT ADVANCES For a long time, PTPs were considered constitutively active housekeeping enzymes. This view has changed substantially over the last two decades, and the PTP family is now recognized as a group of tightly and flexibly regulated fundamental enzymes. In addition to the conventional ways in which they are regulated, including noncovalent interactions, phosphorylation, and oxidation, the evidence that has accumulated during the past two decades suggests that many of these enzymes are also modulated by gasotransmitters, namely by nitric oxide (NO) and hydrogen sulfide (H2S). CRITICAL ISSUES The specificity and selectivity of the methods used to detect nitrosylation and sulfhydration remains to be corroborated, because several researchers raised the issue of false-positive results, particularly when using the most widespread biotin switch method. Further development of robust and straightforward proteomic methods is needed to further improve our knowledge of the full extent of the gasotransmitters-mediated changes in PTP activity, selectivity, and specificity. FURTHER DIRECTIONS: Results of the hitherto performed studies on gasotransmitter-mediated PTP signaling await translation into clinical medicine and pharmacotherapeutics. In addition to directly affecting the activity of particular PTPs, the use of reversible S-nitrosylation as a protective mechanism against oxidative stress should be of high interest.
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Affiliation(s)
- Petr Heneberg
- Third Faculty of Medicine, Charles University in Prague , Prague, Czech Republic
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6
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Matiollo C, Ecco G, Menegatti ACO, Razzera G, Vernal J, Terenzi H. S-nitrosylation of Mycobacterium tuberculosis tyrosine phosphatase A (PtpA) induces its structural instability. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1834:191-6. [PMID: 23102706 DOI: 10.1016/j.bbapap.2012.10.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 10/04/2012] [Accepted: 10/07/2012] [Indexed: 02/06/2023]
Abstract
S-nitrosylation is associated with signal transduction and microbicidal activity of nitric oxide (NO). We have recently described the S-nitrosylation of Mycobacterium tuberculosis protein tyrosine phosphatase A, PtpA, an enzyme that plays an important role in mycobacteria survival inside macrophages. This post-translational modification decreases the activity of the enzyme upon modification of a single Cys residue, C53. The aim of the present work was the investigation of the effect of S-nitrosylation in PtpA kinetic parameters, thermal stability and structure. It was observed that the K(M) of nitrosylated PtpA was similar to its unmodified form, but the V(max) was significantly reduced. In contrast, treatment of PtpA C53A with GSNO, did not alter either K(M) or V(max). These results confirmed that PtpA S-nitrosylation occurs specifically in the non-catalytic C53 and that this modification does not affect substrate affinity. Using circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy techniques it was shown that PtpA S-nitrosylation decreased protein thermal stability and promoted a local effect in the surroundings of the C53 residue, which interfered in both protein stability and function.
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Affiliation(s)
- Camila Matiollo
- Centro de Biologia Molecular Estrutural-INBEB, Departamento de Bioquímica, CCB, Universidade Federal de Santa Catarina, Florianópolis, Brazil
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7
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Zhang HH, Feng L, Wang W, Magness RR, Chen DB. Estrogen-responsive nitroso-proteome in uterine artery endothelial cells: role of endothelial nitric oxide synthase and estrogen receptor-β. J Cell Physiol 2011; 227:146-59. [PMID: 21374595 DOI: 10.1002/jcp.22712] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Covalent adduction of a NO moiety to cysteines (S-nitrosylation or SNO) is a major route for NO to directly regulate protein functions. In uterine artery endothelial cells (UAEC), estradiol-17β (E2) rapidly stimulated protein SNO that maximized within 10-30 min post-E2 exposure. E2-bovine serum albumin stimulated protein SNO similarly. Stimulation of SNO by both was blocked by ICI 182, 780, implicating mechanisms linked to specific estrogen receptors (ERs) localized on the plasma membrane. E2-induced protein SNO was attenuated by selective ERβ, but not ERα, antagonists. A specific ERβ but not ERα agonist was able to induce protein SNO. Overexpression of ERβ, but not ERα, significantly enhanced E2-induced SNO. Overexpression of both ERs increased basal SNO, but did not further enhance E2-stimulated SNO. E2-induced SNO was inhibited by N-nitro-L-arginine-methylester and specific endothelial NO synthase (eNOS) siRNA. Thus, estrogen-induced SNO is mediated by endogenous NO via eNOS and mainly ERβ in UAEC. We further analyzed the nitroso-proteomes by CyDye switch technique combined with two-dimensional (2D) fluorescence difference gel electrophoresis. Numerous nitrosoprotein (spots) were visible on the 2D gel. Sixty spots were chosen and subjected to matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Among the 54 identified, nine were novel SNO-proteins, 32 were increased, eight were decreased, and the rest were unchanged by E2. Tandom MS identified Cys139 as a specific site for SNO in GAPDH. Pathway analysis of basal and estrogen-responsive nitroso-proteomes suggested that SNO regulates diverse protein functions, directly implicating SNO as a novel mechanism for estrogen to regulate uterine endothelial function and thus uterine vasodilatation.
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Affiliation(s)
- Hong-hai Zhang
- Department of Obstetrics and Gynecology, University of California-Irvine, Irvine, California 92697, USA
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8
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Adverse effects of simulated hyper- and hypo-phosphatemia on endothelial cell function and viability. PLoS One 2011; 6:e23268. [PMID: 21858050 PMCID: PMC3153490 DOI: 10.1371/journal.pone.0023268] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Accepted: 07/14/2011] [Indexed: 02/06/2023] Open
Abstract
Background Dysregulaiton of phosphate homeostasis as occurs in chronic kidney disease is associated with cardiovascular complications. It has been suggested that both hyperphosphatemia and hypophosphatemia can cause cardiovascular disease. The molecular mechanisms by which high or low serum phosphate levels adversely affect cardiovascular function are poorly understood. The purpose of this study was to explore the mechanisms of endothelial dysfunction in the presence of non-physiologic phosphate levels. Methodology/Principal Findings We studied the effects of simulated hyper- and hypophosphatemia in human umbilical vein endothelial cells in vitro. We found both simulated hyperphosphatemia and hypophosphatemia decrease eNOS expression and NO production. This was associated with reduced intracellular calcium, increased protein kinase C β2 (PKCβ2), reduced cell viability, and increased apoptosis. While simulated hyperphosphatemia was associated with decreased Akt/p-Akt, Bcl-xl/Bax ratios, NFkB-p65 and p-Erk abundance, simulated hypophosphatemia was associated with increased Akt/p-Akt and Bcl-xl/Bax ratios and p-Mek, p38, and p-p38 abundance. Conclusions/Significance This is the first demonstration of endothelial dysfunction with hypophosphatemia. Our data suggests that both hyperphosphatemia and hypophosphatemia decrease eNOS activity via reduced intracellular calcium and increased PKCβ2. Hyperphosphatemia also appears to reduce eNOS transcription via reduced signaling through PI3K/Akt/NF-kB and MAPK/NF-kB pathways. On the other hand, hypophosphatemia appears to activate these pathways. Our data provides the basis for further studies to elucidate the relationship between altered phosphate homeostasis and cardiovascular disease. As a corollary, our data suggests that the level of phosphate in the culture media, if not in the physiologic range, may inadvertently affect experimental results.
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9
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Ecco G, Vernal J, Razzera G, Martins PA, Matiollo C, Terenzi H. Mycobacterium tuberculosis tyrosine phosphatase A (PtpA) activity is modulated by S-nitrosylation. Chem Commun (Camb) 2010; 46:7501-3. [DOI: 10.1039/c0cc01704c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Abstract
The identification of nitric oxide ((*)NO) as an endogenously produced free radical mediator of endothelial-dependent relaxation and host defense has fundamentally changed concepts of cell signal transduction. Ligand-receptor oriented paradigms of cell signaling were originally centered on the concept of a high affinity and specific interaction between a ligand and its receptor, resulting in the activation of secondary signaling events such as gene expression or modulation of catalytic protein function. While (*)NO ligation of the heme iron of soluble guanylate cyclase is consistent with this perspective, the readily diffusible and broadly reactive (*)NO is increasingly appreciated to react with a vast array of target molecules that mediate paracrine vasodilator actions, inhibition of thrombosis and neointimal proliferation, and both pro- and antiinflammatory signaling reactions that are not affected by inhibitors of soluble guanylate cyclase. There is an expanding array of functionally significant "off target" collateral reactions mediated by (*)NO that are guanylate cyclase-independent and rather are dictated by anatomic distribution and the formation of secondary (*)NO-derived species. These reactions are a critical element of redox-regulated signaling and are addressed herein in the context of the oxidation of unsaturated fatty acids to vascular and inflammatory signaling mediators. Because of their abundance and the intrinsic reactivity of unsaturated lipid intermediates and eicosanoid metabolism enzymes with (*)NO and other oxides of nitrogen, lipid signaling mechanisms are a significant target for regulation by (*)NO in the vascular compartment. This convergence of (*)NO and lipid signaling pathways thus adds another level of regulation to physiological responses such as vasodilation, thrombosis, and inflammation. Herein, interactions between (*)NO and lipid signaling events are placed in the context of cardiovascular regulation.
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Affiliation(s)
- Volker Rudolph
- Department of Pharmacology & Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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11
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Janssen-Heininger YMW, Mossman BT, Heintz NH, Forman HJ, Kalyanaraman B, Finkel T, Stamler JS, Rhee SG, van der Vliet A. Redox-based regulation of signal transduction: principles, pitfalls, and promises. Free Radic Biol Med 2008; 45:1-17. [PMID: 18423411 PMCID: PMC2453533 DOI: 10.1016/j.freeradbiomed.2008.03.011] [Citation(s) in RCA: 571] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2007] [Revised: 03/04/2008] [Accepted: 03/11/2008] [Indexed: 12/15/2022]
Abstract
Oxidants are produced as a by-product of aerobic metabolism, and organisms ranging from prokaryotes to mammals have evolved with an elaborate and redundant complement of antioxidant defenses to confer protection against oxidative insults. Compelling data now exist demonstrating that oxidants are used in physiological settings as signaling molecules with important regulatory functions controlling cell division, migration, contraction, and mediator production. These physiological functions are carried out in an exquisitely regulated and compartmentalized manner by mild oxidants, through subtle oxidative events that involve targeted amino acids in proteins. The precise understanding of the physiological relevance of redox signal transduction has been hampered by the lack of specificity of reagents and the need for chemical derivatization to visualize reversible oxidations. In addition, it is difficult to measure these subtle oxidation events in vivo. This article reviews some of the recent findings that illuminate the significance of redox signaling and exciting future perspectives. We also attempt to highlight some of the current pitfalls and the approaches needed to advance this important area of biochemical and biomedical research.
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12
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Hong L, Fast W. Inhibition of human dimethylarginine dimethylaminohydrolase-1 by S-nitroso-L-homocysteine and hydrogen peroxide. Analysis, quantification, and implications for hyperhomocysteinemia. J Biol Chem 2007; 282:34684-92. [PMID: 17895252 DOI: 10.1074/jbc.m707231200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The plasma concentrations of two cardiovascular risk factors, total homocysteine (tHcy) and asymmetric dimethylarginine (ADMA), correlate with decreased levels of endothelium-derived nitric oxide and subsequent endothelial dysfunction. Homocysteine has been proposed to inhibit the catabolic enzyme of ADMA, dimethylarginine dimethylaminohydrolase (DDAH), but the mechanism of this inhibition has not been fully elucidated. Here, the human DDAH isoform-1 (DDAH-1) is heterologously expressed and purified. Cys(274) and His(173) are identified as active site residues and the pH rate dependence is described. Because oxidation of the active site Cys has been suggested as an inhibitory mechanism in patients with hyperhomocysteinemia, the sensitivity of DDAH-1 to inhibition by L-homocysteine, H(2)O(2), and S-nitroso-L-homocysteine is quantified. DDAH-1 is surprisingly insensitive to inactivation by the powerful oxidant, H(2)O(2) (0.088 M(-1) s(-1)), possibly because of a substrate-assisted mechanism that allows the active site cysteine to remain predominantly protonated and less reactive in the resting enzyme. In contrast, DDAH-1 is sensitive to inactivation by S-nitroso-L-homocysteine (3.79 M(-1) s(-1)). This work illustrates how a particular catalytic mechanism can result in selective redox regulation and has possible implications for hyperhomocysteinemia.
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Affiliation(s)
- Lin Hong
- Division of Medicinal Chemistry, College of Pharmacy, and Texas Institute for Drug and Diagnostic Development, University of Texas, Austin, Texas 78712, USA
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13
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Braun O, Knipp M, Chesnov S, Vasák M. Specific reactions of S-nitrosothiols with cysteine hydrolases: A comparative study between dimethylargininase-1 and CTP synthetase. Protein Sci 2007; 16:1522-34. [PMID: 17600152 PMCID: PMC2203367 DOI: 10.1110/ps.062718507] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
S-Transnitrosation is an important bioregulatory process whereby NO(+) equivalents are transferred between S-nitrosothiols and Cys of target proteins. This reaction proceeds through a common intermediate R-S-N(O(-))-S-R' and it has been proposed that products different from S-nitrosothiols may be formed in protein cavities. Recently, we have reported on the formation of such a product, an N-thiosulfoximide, at the active site of the Cys hydrolase dimethylargininase-1 (DDAH-1) upon reaction with S-nitroso-l-homocysteine (HcyNO). Here we have addressed the question of whether this novel product can also be formed with the endogenously occurring S-nitrosothiols S-nitroso-l-cysteine (CysNO) and S-nitrosoglutathione (GSNO). Further, to explore the reason responsible for the unique formation of an N-thiosulfoximide in DDAH-1 we have expanded these studies to cytidine triphosphate synthetase (CTPS), which shows a similar active site architecture. ESI-MS and activity measurements showed that the bulky GSNO does not react with both enzymes. In contrast, S-nitrosylation of the active site Cys occurred in DDAH-1 with CysNO and in CTPS with CysNO and HcyNO. Although kinetic analysis indicated that these compounds act as specific irreversible inhibitors, no N-thiosulfoximide was formed. The reasons likely responsible for the absence of the N-thiosulfoximide formation are discussed using molecular models of DDAH-1 and CTPS. In tissue extracts DDAH was inhibited only by HcyNO, with an IC(50) value similar to that of the isolated protein. Biological implications of these studies for the function of both enzymes are discussed.
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Affiliation(s)
- Oliver Braun
- Department of Biochemistry, University of Zürich, CH-8057 Zürich, Switzerland
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14
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Spurny R, Abdoulrahman K, Janda L, Rünzler D, Köhler G, Castañón MJ, Wiche G. Oxidation and Nitrosylation of Cysteines Proximal to the Intermediate Filament (IF)-binding Site of Plectin. J Biol Chem 2007; 282:8175-87. [PMID: 17224453 DOI: 10.1074/jbc.m608473200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As an intermediate filament (IF)-based cytolinker protein, plectin plays a key role in the maintenance of cellular cytoarchitecture and serves at the same time as a scaffolding platform for signaling cascades. Consisting of six structural repeats (R1-6) and harboring binding sites for different IF proteins and proteins involved in signaling, the plectin C-terminal domain is of strategic functional importance. Depending on the species, it contains at least 13 cysteines, 4 of which reside in the R5 domain. To investigate the structural and biological functions of R5 cysteines, we used cysteine-to-serine mutagenesis and spectroscopic, biochemical, and functional analyses. Urea-induced unfolding experiments indicated that wild-type R5 in the oxidized, disulfide bond-mediated conformation was more stable than its cysteine-free mutant derivative. The binding affinity of R5 for vimentin was significantly higher, however, when the protein was in the reduced, more relaxed conformation. Of the four R5 cysteines, one (Cys4) was particularly reactive as reflected by its ability to form disulfide bridges with R5 Cys1 and to serve as a target for nitrosylation in vitro. Using immortalized endothelial cell cultures from mice, we show that endogenous plectin is nitrosylated in vivo, and we found that NO donor-induced IF collapse proceeds dramatically faster in plectin-deficient compared with wild-type cells. Our data suggest an antagonistic role of plectin in nitrosylation (oxidative stress)-mediated alterations of IF cytoarchitecture and a possible role of R5 Cys4 as a regulatory switch.
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Affiliation(s)
- Radovan Spurny
- Department of Molecular Cell Biology, Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
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15
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Shami PJ, Saavedra JE, Bonifant CL, Chu J, Udupi V, Malaviya S, Carr BI, Kar S, Wang M, Jia L, Ji X, Keefer LK. Antitumor activity of JS-K [O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate] and related O2-aryl diazeniumdiolates in vitro and in vivo. J Med Chem 2006; 49:4356-66. [PMID: 16821795 DOI: 10.1021/jm060022h] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The literature provides evidence that metabolic nitric oxide (NO) release mediates the cytotoxic activities (against human leukemia and prostate cancer xenografts in mice) of JS-K, a compound of structure R(2)N-N(O)=NO-Ar for which R(2)N is 4-(ethoxycarbonyl)piperazin-1-yl and Ar is 2,4-dinitrophenyl. Here we present comparative data on the potencies of JS-K and 41 other O(2)-arylated diazeniumdiolates as inhibitors of HL-60 human leukemia cell proliferation, as well as in the NCI 51-cell-line screen for six of them. The data show JS-K to be the most potent of the 42 in both screens and suggest that other features of its structure and metabolism besides NO release may contribute importantly to its activity. Results with control compounds implicate JS-K's arylating ability, and the surprisingly low IC(50) value of the N-(ethoxycarbonyl)piperazine byproduct of NO release suggests a role for the R(2)N moiety. In addition to the above-mentioned in vivo activities, JS-K is shown here to be carcinostatic in a rat liver cancer model.
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Affiliation(s)
- Paul J Shami
- Department of Internal Medicine, Division of Medical Oncology, University of Utah, Salt Lake City, 84112, USA
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Hess DT, Matsumoto A, Kim SO, Marshall HE, Stamler JS. Protein S-nitrosylation: purview and parameters. Nat Rev Mol Cell Biol 2005; 6:150-66. [PMID: 15688001 DOI: 10.1038/nrm1569] [Citation(s) in RCA: 1596] [Impact Index Per Article: 84.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
S-nitrosylation, the covalent attachment of a nitrogen monoxide group to the thiol side chain of cysteine, has emerged as an important mechanism for dynamic, post-translational regulation of most or all main classes of protein. S-nitrosylation thereby conveys a large part of the ubiquitous influence of nitric oxide (NO) on cellular signal transduction, and provides a mechanism for redox-based physiological regulation.
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Affiliation(s)
- Douglas T Hess
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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17
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Dupret JM, Dairou J, Atmane N, Rodrigues-Lima F. Inactivation of Human Arylamine N‐Acetyltransferase 1 by Hydrogen Peroxide and Peroxynitrite. Methods Enzymol 2005; 400:215-29. [PMID: 16399351 DOI: 10.1016/s0076-6879(05)00012-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Arylamine N-acetyltransferases (NAT) are xenobiotic-metabolizing enzymes responsible for the acetylation of many arylamine and heterocyclic amines. They therefore play an important role in the detoxification and activation of numerous drugs and carcinogens. Two closely related isoforms (NAT1 and NAT2) have been described in humans. NAT2 is present mainly in the liver and intestine, whereas NAT1 is found in a wide range of tissues. Interindividual variations in NAT genes have been shown to be a potential source of pharmacological and/or pathological susceptibility. Evidence now shows that redox conditions may also contribute to overall NAT activity. This chapter summarizes current knowledge on human NAT1 regulation by reactive oxygen and nitrogen species.
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Affiliation(s)
- Jean-Marie Dupret
- CNRS-Unite Mixte de Recherche 7000, Faculte de Medecine, Pitie-Salpetriere, Paris, France
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18
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Dufresne C, Roy P, Wang Z, Asante-Appiah E, Cromlish W, Boie Y, Forghani F, Desmarais S, Wang Q, Skorey K, Waddleton D, Ramachandran C, Kennedy BP, Xu L, Gordon R, Chan CC, Leblanc Y. The development of potent non-peptidic PTP-1B inhibitors. Bioorg Med Chem Lett 2004; 14:1039-42. [PMID: 15013019 DOI: 10.1016/j.bmcl.2003.11.048] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2003] [Accepted: 11/14/2003] [Indexed: 11/18/2022]
Abstract
The SAR from our peptide libraries was exploited to design a series of potent deoxybenzoin PTP-1B inhibitors. The introduction of an ortho bromo substituent next to the difluoromethylphosphonate warhead gave up to 20-fold increase in potency compared to the desbromo analogues. In addition, these compounds were orally bioavailable and active in the animal models of non-insulin dependent diabetes mellitus (NIDDM).
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Affiliation(s)
- Claude Dufresne
- Department of Medicinal Chemistry, Merck Frosst Centre for Therapeutic Research, PO Box 1005, Pointe-Claire, Dorval, Canada H9R 4P8.
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19
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Ren Z, Kar S, Wang Z, Wang M, Saavedra JE, Carr BI. JS-K, a novel non-ionic diazeniumdiolate derivative, inhibits Hep 3B hepatoma cell growth and induces c-Jun phosphorylation via multiple MAP kinase pathways. J Cell Physiol 2003; 197:426-34. [PMID: 14566972 DOI: 10.1002/jcp.10380] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
JS-K, a non-ionic diazeniumdiolate derivative, is capable of arylating nucleophiles and spontaneously generating nitric oxide (NO) at physiological pH. This recently synthesized low molecular weight compound is shown here to be an inhibitor of cell growth with concomitant activation of mitogen-activated protein kinase (MAPK) members ERK, JNK, and p38 and their downstream effectors c-Jun and AP-1. Inhibitors of these MAPK pathways abrogated the growth inhibitory actions of JS-K. In addition to the well-described actions of JNK as a kinase for c-Jun, we show that c-Jun is also an ERK target. Furthermore, JS-K generated NO in culture and NO inhibitors antagonized both MAPK induction and the growth inhibitory effects of JS-K. These results suggest two possible mechanisms for the mediation of JS-K growth inhibitory actions, namely NO-induction of MAPK pathway constituents as well as possible arylation reactions. The data support the idea that prolonged MAPK activation by JS-K action is important in mediating its growth-inhibitory actions. JS-K thus represents a promising platform for novel growth inhibitory analog synthesis.
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Affiliation(s)
- Zhenggang Ren
- Liver Cancer Center, Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
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20
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Dairou J, Atmane N, Dupret JM, Rodrigues-Lima F. Reversible inhibition of the human xenobiotic-metabolizing enzyme arylamine N-acetyltransferase 1 by S-nitrosothiols. Biochem Biophys Res Commun 2003; 307:1059-65. [PMID: 12878219 DOI: 10.1016/s0006-291x(03)01311-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Human arylamine N-acetyltransferase 1 (NAT1) is a polymorphic phase II xenobiotic-metabolizing enzyme which catalyzes the biotransformation of primary aromatic amines, hydrazine drugs, and carcinogens. Structural and functional studies have shown that the NAT1 and factor XIII transglutaminase catalytic pockets are structurally related with the existence of a conserved catalytic triad (Cys-His-Asp). In addition, it has been reported that factor XIII transglutaminase activity could be regulated by nitric oxide (NO), in particular S-nitrosothiols (RSNO). We thus tested whether NAT1 could be a target of S-nitrosothiols. We show here that human NAT1 is reversibly inactivated by S-nitrosothiols such as SNAP (S-nitroso-N-acetyl-DL-penicillamine). A second-order rate constant for the inactivation of NAT1 by SNAP was determined (k(inact)=270M(-1)min(-1)) and shown to be in the same range of values reported for other enzymes. The inhibition of NAT1 by S-nitrosothiols was reversed by dithiothreitol and reduced glutathione, but not by ascorbate. As reported for some reactive cysteine-containing enzymes, our results suggest that inactivation of NAT1 by S-nitrosothiols is due to direct attack of the highly reactive cysteine residue in the enzyme active site on the sulfur of S-nitrosothiols to form a mixed disulfide between these NO-derived oxidants and NAT1. Finally, our findings suggest that, in addition to the polymorphic-dependent variation of NAT1 activity, NO-derived oxidants, in particular S-nitrosothiols, could also regulate NAT1 activity.
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Affiliation(s)
- Julien Dairou
- CNRS-UMR 7000, Faculté de Médecine Pitié-Salpêtrière, 105 boulevard de l'Hôpital, 75013 Paris, France
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21
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Giles NM, Watts AB, Giles GI, Fry FH, Littlechild JA, Jacob C. Metal and redox modulation of cysteine protein function. CHEMISTRY & BIOLOGY 2003; 10:677-93. [PMID: 12954327 DOI: 10.1016/s1074-5521(03)00174-1] [Citation(s) in RCA: 321] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In biological systems, the amino acid cysteine combines catalytic activity with an extensive redox chemistry and unique metal binding properties. The interdependency of these three aspects of the thiol group permits the redox regulation of proteins and metal binding, metal control of redox activity, and ligand control of metal-based enzyme catalysis. Cysteine proteins are therefore able to act as "redox switches," to sense concentrations of oxidative stressors and unbound zinc ions in the cytosol, to provide a "storage facility" for excess metal ions, to control the activity of metalloproteins, and to take part in important regulatory and signaling pathways. The diversity of cysteine's multiple roles in vivo is equally as fascinating as it is promising for future biochemical and pharmacological research.
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Affiliation(s)
- Niroshini M Giles
- School of Biological and Chemical Sciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
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22
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Spallarossa A, Forlani F, Pagani S, Salvati L, Visca P, Ascenzi P, Bolognesi M, Bordo D. Inhibition of Azotobacter vinelandii rhodanese by NO-donors. Biochem Biophys Res Commun 2003; 306:1002-7. [PMID: 12821142 DOI: 10.1016/s0006-291x(03)01067-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitric oxide (NO) is a versatile regulatory molecule that affects enzymatic activity through chemical modification of reactive amino acid residues (e.g., Cys and Tyr) and by binding to metal centers. In the present study, the inhibitory effect of the NO-donors S-nitroso-glutathione (GSNO), (+/-)E-4-ethyl-2-[E-hydroxyimino]-5-nitro-3-hexenamide (NOR-3), and S-nitroso-N-acetyl-penicillamine (SNAP) on the catalytic activity of Azotobacter vinelandii rhodanese (RhdA) has been investigated. GSNO, NOR-3, and SNAP inhibit RhdA sulfurtransferase activity in a concentration- and time-dependent fashion. The absorption spectrum of the NOR-3-treated RhdA displays a maximum at 335 nm, indicating NO-mediated S-nitrosylation. RhdA inhibition by NO-donors correlates with S-nitrosothiol formation. The reducing agent dithiothreitol prevents RhdA inhibition by NO-donors, fully restores the catalytic activity, and reverts the NOR-3-induced RhdA absorption spectrum to that of the active enzyme. These results indicate that RhdA inhibition occurs via NO-mediated S-nitrosylation of the unique Cys230 catalytic residue.
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Affiliation(s)
- Andrea Spallarossa
- Dipartimento di Scienze Farmaceutiche, Università di Genova, Via Benedetto XV 3, I-16132 Genoa, Italy
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23
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Li S, Whorton AR. Regulation of protein tyrosine phosphatase 1B in intact cells by S-nitrosothiols. Arch Biochem Biophys 2003; 410:269-79. [PMID: 12573287 DOI: 10.1016/s0003-9861(02)00696-3] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein tyrosine phosphatases (PTPases) contain an active site cysteine which when oxidized leads to loss of phosphatase activity and accumulation of phosphoproteins. For example, oxidants produced following EGF stimulation inhibit PTP1B and enhance EGF receptor phosphorylation. Because NO-derived species also modify reactive thiols, we postulated that NO would reversibly inhibit PTP1B. In our studies we exposed A431 or Jurkat cells to NO donors and measured PTP1B activity or used 3-maleimidylpropionylbiocytin (MPB) to measure thiol redox status. Nitrosothiols led to a rapid inhibition of PTP1B through a mechanism that was greatly enhanced by addition of cysteine to the medium. Analysis of thiol oxidation status using immunoprecipitated PTP1B showed modification consistent with loss of activity. Both enzyme inhibition and modification were reversible in intact cells or after addition of DTT to cell lysates. While DTT reversed oxidation, ascorbate did not, suggesting that formation of a mixed disulfide (possibly glutathionylation) rather than S-nitrosylation accounts for PTP1B inhibition. Importantly, PTP1B inhibition by nitrosothiols led to EGF receptor phosphorylation even in the absence of exogenously added EGF. These findings suggest an important role for NO in modulating signaling pathways since inhibition of PTPases could potentially enhance or prolong activity of phosphoproteins.
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Affiliation(s)
- Sheng Li
- Department of Pharmacology and Cancer Biology, C138B LSRC, Box 3813, Duke University Medical Center, Durham, NC 27710-0001, USA
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24
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Abstract
Nitric oxide (NO)-mediated nitrosation reactions are involved in cell signaling and pathology. Recent efforts have focused on elucidating the role of S-nitrosothiols (RSNO) in different biological systems, including human plasma, where they are believed to represent a transport and buffer system that controls intercellular NO exchange. Although RSNOs have been implicated in cardiovascular disease processes, it is yet unclear what their true physiological concentration is, whether a change in plasma concentration is causally related to the underlying pathology or purely epiphenomenological, and to what extent other nitrosyl adducts may be formed under the same conditions. Therefore, using gas phase chemiluminescence and liquid chromatography we sought to quantify the basal plasma levels of NO-related metabolites in 18 healthy volunteers. We find that in addition to the oxidative products of NO metabolism, nitrite (0.20 +/- 0.02 micromol/l nitrite) and nitrate (14.4 +/- 1.7 micromol/l), on average human plasma contains an approximately 5-fold higher concentration of N-nitroso species (32.3 +/- 5.0 nmol/l) than RSNOs (7.2 +/- 1.1 nmol/l). Both N- and S-nitroso moieties appear to be associated with the albumin fraction. This is the first report on the constitutive presence of a high-molecular-weight N-nitroso compound in the human circulation, raising the question as to its origin and potential physiological role. Our findings may not only have important implications for the transport of NO in vivo, but also for cardiovascular disease diagnostics and the risk assessment of nitrosamine-related carcinogenesis in man.
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Affiliation(s)
- Tienush Rassaf
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
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25
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Akhter S, Vignini A, Wen Z, English A, Wang PG, Mutus B. Evidence for S-nitrosothiol-dependent changes in fibrinogen that do not involve transnitrosation or thiolation. Proc Natl Acad Sci U S A 2002; 99:9172-7. [PMID: 12089331 PMCID: PMC123113 DOI: 10.1073/pnas.142136499] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2002] [Indexed: 11/18/2022] Open
Abstract
S-nitrosoglutathione (GSNO, 50 microM) inhibited the initial rate of thrombin-catalyzed human and bovine fibrinogen polymerization by approximately 50% to 68% respectively. Inhibition was also observed with other structurally varied S-nitrosothiols (RSNOs) including sugar derivatives of S-nitroso-N-acetylpenicillamine (SNAP). The fact that the same concentration of GSNO had no effect on thrombin-dependent hydrolysis of tosylglycylprolylarginine-4-nitroanilide acetate suggested that this inhibition was due to GSNO-induced changes in fibrinogen structure. This result was confirmed by CD spectroscopy where GSNO or S-nitrosohomocysteine increased the alpha-helical content of fibrinogen by approximately 15% and 11%, respectively. S-carboxymethylamido derivatives of glutathione or homocysteine had no effect on the fibrinogen secondary structure. The GSNO-dependent secondary structural effects were reversed on gel filtration chromatography, suggesting that the effects were allosteric. Further evidence for fibrinogen-GSNO interactions was obtained from GSNO-dependent quenching of the intrinsic fibrinogen Trp fluorescence and the perturbation of the GSNO circular dichroic absorbance as a function of [fibrinogen]. The K(d)s of 3 to 10 microM for fibrinogen-GSNO interactions with a stoichiometry of 2:1 (GSNO:fibrinogen) were estimated from isothermal titration calorimetry and fluorescence quenching, respectively. These results suggest that RSNOs induce changes to fibrinogen structure by interacting at specific aromatic rich domains. Three such putative RSNO-binding domains have been identified in the unordered, aromatic residue-rich C-termini of the alpha-chains of fibrinogen.
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Affiliation(s)
- Shirin Akhter
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada N9B
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26
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Abstract
Caspases are a family of cysteine proteases activated during apoptosis. In cultured human endothelial cells, physiological levels of NO prevent apoptosis and interfere with the activation of the caspase cascade. Previous studies have demonstrated that NO inhibits the activity of caspase-3 by S-nitrosylation of the enzyme. In this study, the inhibitory effect of a new class of NO donors. N-nitrosoaniline derivatives, were examined against caspase-3. Initially eight small molecule inhibitors bearing N-nitroso moieties were assayed. It was found that the presence of an electron-donating group on the phenyl ring led to better inhibitory potency, a trend consistent with the results from the previous papain studies. Based on the analysis of the enzyme and substrates' structures, two peptidyl N-nitrosoaniline inhibitors [Ac-DVAD-NNO (1) and Ac-DV-AMO (2)] were designed and synthesized. Both compounds exhibited enhanced inhibitory potency against caspase-3.
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Affiliation(s)
- Z Guo
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
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27
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Xian M, Wang QM, Chen X, Wang K, Wang PG. S-nitrosothiols as novel, reversible inhibitors of human rhinovirus 3C protease. Bioorg Med Chem Lett 2000; 10:2097-100. [PMID: 10999479 DOI: 10.1016/s0960-894x(00)00420-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Human rhinovirus (HRV) 3C protease was inactivated by a series of S-nitrosothiols. These compounds exhibited different inhibitory activities in a time- and concentration-dependent manner with second-order rate constants (kinact/K(I)) ranging from 131 to 5360 M(-1) min(-1). The inactive enzyme could be re-activated by DTT, GSH and ascorbate, which indicated the inactivation mechanism was through an S-transnitrosylation process.
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Affiliation(s)
- M Xian
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
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28
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Xian M, Chen X, Liu Z, Wang K, Wang PG. Inhibition of papain by S-nitrosothiols. Formation of mixed disulfides. J Biol Chem 2000; 275:20467-73. [PMID: 10779505 DOI: 10.1074/jbc.m001054200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
S-Nitrosylation of protein thiols is one of the cellular regulatory mechanisms induced by NO. The cysteine protease papain has a critical thiol residue (Cys(25)). It has been demonstrated that NO or NO donors such as sodium nitroprusside and N-nitrosoaniline derivatives can reversibly inhibit this enzyme by S-NO bond formation in its active site. In this study, a different regulated mechanism of inactivation was reported using S-nitrosothiols as the NO donor. Five S-nitroso compounds, S-nitroso-N-acetyl-dl-penicillamine, S-nitrosoglutathione, S-nitrosocaptopril, glucose-S-nitroso-N-acetyl-dl-penicillamine-2, and the S-nitroso tripeptide acetyl-Phe-Gly-S-nitrosopenicillamine, exhibited different inhibitory activities toward the enzyme in a time- and concentration-dependent manner with second-order rate constants (k(i)/K(I)) ranging from 8.9 to 17.2 m(-1) s(-1). The inhibition of papain by S-nitrosothiol was rapidly reversed by dithiothreitol, but not by ascorbate, which could reverse the inhibition of papain by NOBF(4). Incubation of the enzyme with a fluorescent S-nitroso probe (S-nitroso-5-dimethylaminonaphthalene-1-sulfonyl) resulted in the appearance of fluorescence of the protein, indicating the formation of a thiol adduct. Moreover, S-transnitrosylation in the incubation of S-nitroso inactivators with papain was excluded. These results suggest that inactivation of papain by S-nitrosothiols is due to a direct attack of the highly reactive thiolate (Cys(25)) in the enzyme active site on the sulfur of S-nitrosothiols to form a mixed disulfide between the inactivator and papain.
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Affiliation(s)
- M Xian
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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