RESUMO
Sixteen ovarian tumor (OTU) family deubiquitinases (DUBs) exist in humans, and most members regulate cell-signaling cascades. Several OTU DUBs were reported to be ubiquitin (Ub) chain linkage specific, but comprehensive analyses are missing, and the underlying mechanisms of linkage specificity are unclear. Using Ub chains of all eight linkage types, we reveal that most human OTU enzymes are linkage specific, preferring one, two, or a defined subset of linkage types, including unstudied atypical Ub chains. Biochemical analysis and five crystal structures of OTU DUBs with or without Ub substrates reveal four mechanisms of linkage specificity. Additional Ub-binding domains, the ubiquitinated sequence in the substrate, and defined S1' and S2 Ub-binding sites on the OTU domain enable OTU DUBs to distinguish linkage types. We introduce Ub chain restriction analysis, in which OTU DUBs are used as restriction enzymes to reveal linkage type and the relative abundance of Ub chains on substrates.
Assuntos
Endopeptidases/química , Endopeptidases/metabolismo , Neoplasias Ovarianas/enzimologia , Ubiquitinação , Catálise , Domínio Catalítico , Cristalografia por Raios X , Endopeptidases/genética , Feminino , Humanos , Modelos Moleculares , Neoplasias Ovarianas/metabolismo , Estrutura Terciária de Proteína , Tioléster Hidrolases/química , Tioléster Hidrolases/metabolismo , Ubiquitinas/metabolismoRESUMO
Serine hydroxymethyltransferase 2 (SHMT2) regulates one-carbon transfer reactions that are essential for amino acid and nucleotide metabolism, and uses pyridoxal-5'-phosphate (PLP) as a cofactor. Apo SHMT2 exists as a dimer with unknown functions, whereas PLP binding stabilizes the active tetrameric state. SHMT2 also promotes inflammatory cytokine signalling by interacting with the deubiquitylating BRCC36 isopeptidase complex (BRISC), although it is unclear whether this function relates to metabolism. Here we present the cryo-electron microscopy structure of the human BRISC-SHMT2 complex at a resolution of 3.8 Å. BRISC is a U-shaped dimer of four subunits, and SHMT2 sterically blocks the BRCC36 active site and inhibits deubiquitylase activity. Only the inactive SHMT2 dimer-and not the active PLP-bound tetramer-binds and inhibits BRISC. Mutations in BRISC that disrupt SHMT2 binding impair type I interferon signalling in response to inflammatory stimuli. Intracellular levels of PLP regulate the interaction between BRISC and SHMT2, as well as inflammatory cytokine responses. These data reveal a mechanism in which metabolites regulate deubiquitylase activity and inflammatory signalling.
Assuntos
Enzimas Desubiquitinantes/metabolismo , Glicina Hidroximetiltransferase/metabolismo , Interferon Tipo I/imunologia , Complexos Multienzimáticos/imunologia , Complexos Multienzimáticos/metabolismo , Transdução de Sinais/imunologia , Microscopia Crioeletrônica , Enzimas Desubiquitinantes/antagonistas & inibidores , Enzimas Desubiquitinantes/química , Enzimas Desubiquitinantes/ultraestrutura , Glicina Hidroximetiltransferase/ultraestrutura , Células HEK293 , Humanos , Inflamação/imunologia , Modelos Moleculares , Complexos Multienzimáticos/química , Complexos Multienzimáticos/genética , Mutação , Ligação Proteica , Multimerização Proteica , Estrutura Quaternária de Proteína , Fosfato de Piridoxal/metabolismoRESUMO
Deubiquitinating enzymes (DUBs) control vital processes in eukaryotes by hydrolyzing ubiquitin adducts. Their activities are tightly regulated, but the mechanisms remain elusive. In particular, the DUB UCH-L5 can be either activated or inhibited by conserved regulatory proteins RPN13 and INO80G, respectively. Here we show how the DEUBAD domain in RPN13 activates UCH-L5 by positioning its C-terminal ULD domain and crossover loop to promote substrate binding and catalysis. The related DEUBAD domain in INO80G inhibits UCH-L5 by exploiting similar structural elements in UCH-L5 to promote a radically different conformation, and employs molecular mimicry to block ubiquitin docking. In this process, large conformational changes create small but highly specific interfaces that mediate activity modulation of UCH-L5 by altering the affinity for substrates. Our results establish how related domains can exploit enzyme conformational plasticity to allosterically regulate DUB activity. These allosteric sites may present novel insights for pharmaceutical intervention in DUB activity.
Assuntos
Proteínas de Ligação a DNA/química , Glicoproteínas de Membrana/química , Estrutura Terciária de Proteína , Ubiquitina Tiolesterase/química , Sequência de Aminoácidos , Cristalografia por Raios X , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Ativação Enzimática , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Mutação , Ligação Proteica , Estrutura Secundária de Proteína , Homologia de Sequência de Aminoácidos , Especificidade por Substrato , Ubiquitina/química , Ubiquitina/metabolismo , Ubiquitina Tiolesterase/genética , Ubiquitina Tiolesterase/metabolismoRESUMO
The histone methyltransferase Dot1 is conserved from yeast to human and methylates lysine 79 of histone H3 (H3K79) on the core of the nucleosome. H3K79 methylation by Dot1 affects gene expression and the response to DNA damage, and is enhanced by monoubiquitination of the C-terminus of histone H2B (H2Bub1). To gain more insight into the functions of Dot1, we generated genetic interaction maps of increased-dosage alleles of DOT1. We identified a functional relationship between increased Dot1 dosage and loss of the DUB module of the SAGA co-activator complex, which deubiquitinates H2Bub1 and thereby negatively regulates H3K79 methylation. Increased Dot1 dosage was found to promote H2Bub1 in a dose-dependent manner and this was exacerbated by the loss of SAGA-DUB activity, which also caused a negative genetic interaction. The stimulatory effect on H2B ubiquitination was mediated by the N-terminus of Dot1, independent of methyltransferase activity. Our findings show that Dot1 and H2Bub1 are subject to bi-directional crosstalk and that Dot1 possesses chromatin regulatory functions that are independent of its methyltransferase activity.
Assuntos
Histona-Lisina N-Metiltransferase/metabolismo , Histonas/metabolismo , Proteínas Nucleares/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Ubiquitinação , Cromatina/genética , Cromatina/metabolismo , Histona-Lisina N-Metiltransferase/genética , Proteínas Nucleares/genética , Ligação Proteica , Mapas de Interação de Proteínas/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genéticaRESUMO
Promiscuous inhibitors of tyrosine protein kinases, proteases and phosphatases are useful reagents for probing regulatory pathways and stabilizing lysates as well as starting points for the design of more selective agents. Ubiquitination regulates many critical cellular processes, and promiscuous inhibitors of deubiquitinases (DUBs) would be similarly valuable. The currently available promiscuous DUB inhibitors are highly reactive electrophilic compounds that can crosslink proteins. Herein we introduce diarylcarbonate esters as a novel class of promiscuous DUB inhibitors that do not have the liabilities associated with the previously reported compounds. Diarylcarbonates stabilize the high molecular weight ubiquitin pools in cells and lysates. They also elicit cellular phenotypes associated with DUB inhibition, demonstrating their utility in ubiquitin discovery. Diarylcarbonates may also be a useful scaffold for the development of specific DUB inhibitors.
Assuntos
Carbonatos/farmacologia , Enzimas Desubiquitinantes/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Carbonatos/síntese química , Carbonatos/química , Enzimas Desubiquitinantes/metabolismo , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Humanos , Estrutura Molecular , Relação Estrutura-Atividade , Ubiquitinação/efeitos dos fármacosRESUMO
Post-translational modifications of proteins with ubiquitin (Ub) and ubiquitin-like modifiers (Ubls), orchestrated by a cascade of specialized E1, E2 and E3 enzymes, control a wide range of cellular processes. To monitor catalysis along these complex reaction pathways, we developed a cascading activity-based probe, UbDha. Similarly to the native Ub, upon ATP-dependent activation by the E1, UbDha can travel downstream to the E2 (and subsequently E3) enzymes through sequential trans-thioesterifications. Unlike the native Ub, at each step along the cascade, UbDha has the option to react irreversibly with active site cysteine residues of target enzymes, thus enabling their detection. We show that our cascading probe 'hops' and 'traps' catalytically active Ub-modifying enzymes (but not their substrates) by a mechanism diversifiable to Ubls. Our founder methodology, amenable to structural studies, proteome-wide profiling and monitoring of enzymatic activity in living cells, presents novel and versatile tools to interrogate Ub and Ubl cascades.
Assuntos
Sondas Moleculares/farmacologia , Enzimas Ativadoras de Ubiquitina/antagonistas & inibidores , Células HeLa , Humanos , Modelos Moleculares , Sondas Moleculares/síntese química , Sondas Moleculares/química , Estrutura Molecular , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Ubiquitina/metabolismo , Enzimas Ativadoras de Ubiquitina/metabolismoRESUMO
We present the development of a native chemical ligation handle that also functions as a masked electrophile that can be liberated during synthesis when required. This handle can thus be used for the synthesis of complex activity-based probes. We describe the use of this handle in the generation of linkage-specific activity-based deubiquitylating enzyme probes that contain substrate context and closely mimic the native ubiquitin isopeptide linkage. We have generated activity-based probes based on all seven isopeptide-linked diubiquitin topoisomers and demonstrated their structural integrity and ability to label DUBs in a linkage-specific manner.
Assuntos
Corantes Fluorescentes/química , Ubiquitinas/química , Animais , Carbocianinas/química , Domínio Catalítico , Linhagem Celular Tumoral , Eletroforese , Endopeptidases/química , Endopeptidases/metabolismo , Humanos , Camundongos , Especificidade por SubstratoRESUMO
The outcome of cell signaling depends not only on signal strength but also on temporal progression. We use Fluorescence Lifetime Imaging of Resonance Energy Transfer (FLIM/FRET) biosensors to investigate intracellular signaling dynamics. We examined the ß1 receptor-Gαs-cAMP signaling axis using both widefield frequency domain FLIM (fdFLIM) and fast confocal time-correlated single photon counting (TCSPC) setups. Unexpectedly, we observed that fdFLIM revealed transient cAMP responses in HeLa and Cos7 cells, contrasting with sustained responses as detected with TCSPC. Investigation revealed no light-induced effects on cAMP generation or breakdown. Rather, folic acid present in the imaging medium appeared to be the culprit, as its excitation with blue light sensitized degradation of ß1 agonists. Our findings highlight the impact of subtle phototoxicity on experimental outcomes, advocating confocal TCSPC for reliable analysis of response kinetics and stressing the need for full disclosure of chemical formulations by scientific vendors.
RESUMO
Both severe acute respiratory syndrome coronavirus 1 and 2 (SARS-CoV-1 and SARS-CoV-2) encode a papain-like protease (PLpro), which plays a vital role in viral propagation. PLpro accomplishes this function by processing the viral polyproteins essential for viral replication and removing the small proteins, ubiquitin and ISG15 from the host's key immune signaling proteins, thereby preventing the host's innate immune response. Although PLpro from both SARS-CoV-1 and SARS-CoV-2 are structurally highly similar (83% sequence identity), they exhibit functional variability. Hence, to further elucidate the mechanism and aid in drug discovery efforts, the biochemical and kinetic characterization of PLpro is needed. This chapter describes step-by-step experimental procedures for evaluating PLpro activity in vitro using activity-based probes (ABPs) along with fluorescence-based substrates. Herein we describe a step-by-step experimental procedure to assess the activity of PLpro in vitro using a suite of activity-based probes (ABPs) and fluorescent substrates and how they can be applied as fast and yet sensitive methods to calculate kinetic parameters.
Assuntos
COVID-19 , Ubiquitina , Humanos , Ubiquitina/metabolismo , SARS-CoV-2/genética , Proteases Semelhantes à Papaína de Coronavírus , Papaína , Peptídeo Hidrolases/metabolismo , Ubiquitinas/metabolismo , Citocinas/metabolismoRESUMO
A litter of pups: The synthesis and in vitro evaluation of new Pup-based fluorogenic substrates for Dop, the mycobacterial depupylase, are described. A full-length Pup-amidomethylcoumarin conjugate as well as an amino-terminus-truncated analogue exhibited high sensitivity and specificity towards hydrolysis by Dop. The substrates developed here might find application as high-throughput screening assay reagents for the identification of Dop inhibitors.
Assuntos
Amidoidrolases/metabolismo , Proteínas de Bactérias/metabolismo , Corantes Fluorescentes/química , Mycobacterium tuberculosis/efeitos dos fármacos , Ubiquitinas/metabolismo , Fatores de Virulência/metabolismo , Amidoidrolases/antagonistas & inibidores , Sequência de Aminoácidos , Proteínas de Bactérias/antagonistas & inibidores , Biocatálise , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Ensaios de Triagem em Larga Escala , Hidrólise , Cinética , Dados de Sequência Molecular , Peptídeos/síntese química , Peptídeos/química , Peptídeos/metabolismo , Especificidade por Substrato , Ubiquitinas/antagonistas & inibidores , Fatores de Virulência/antagonistas & inibidoresRESUMO
The E1 enzyme Uba6 initiates signal transduction by activating ubiquitin and the ubiquitin-like protein FAT10 in a two-step process involving sequential catalysis of adenylation and thioester bond formation. To gain mechanistic insights into these processes, we determined the crystal structure of a human Uba6/ubiquitin complex. Two distinct architectures of the complex are observed: one in which Uba6 adopts an open conformation with the active site configured for catalysis of adenylation, and a second drastically different closed conformation in which the adenylation active site is disassembled and reconfigured for catalysis of thioester bond formation. Surprisingly, an inositol hexakisphosphate (InsP6) molecule binds to a previously unidentified allosteric site on Uba6. Our structural, biochemical, and biophysical data indicate that InsP6 allosterically inhibits Uba6 activity by altering interconversion of the open and closed conformations of Uba6 while also enhancing its stability. In addition to revealing the molecular mechanisms of catalysis by Uba6 and allosteric regulation of its activities, our structures provide a framework for developing Uba6-specific inhibitors and raise the possibility of allosteric regulation of other E1s by naturally occurring cellular metabolites.
Assuntos
Enzimas Ativadoras de Ubiquitina , Ubiquitina , Catálise , Domínio Catalítico , Humanos , Ubiquitina/metabolismo , Enzimas Ativadoras de Ubiquitina/metabolismo , Ubiquitinas/metabolismoRESUMO
We demonstrate that oxime ligation is an efficient, straightforward, and generally applicable strategy for generating nonhydrolyzable ubiquitin (Ub)-isopeptide isosteres. We synthesized nonhydrolyzable K48- and K63-linked Ub-isopeptide isosteres to investigate the selectivity of deubiquitinating enzymes for specific linkages employing surface plasmon resonance spectroscopy. The results indicate that deubiquitinating enzymes specifically recognize the local peptide sequence flanking Ub-branched lysine residues in target proteins. The described strategy allows the systematic investigation of sequence requirements for substrate selectivity of deubiquitinating enzymes.
Assuntos
Técnicas Biossensoriais/métodos , Endopeptidases/metabolismo , Peptídeos/metabolismo , Ubiquitina/metabolismo , Sequência de Aminoácidos , Modelos Moleculares , Dados de Sequência Molecular , Peptídeos/química , Conformação Proteica , Especificidade por Substrato , Ubiquitina/químicaRESUMO
Viral papain-like cysteine protease (PLpro, NSP3) is essential for SARS-CoV-2 replication and represents a promising target for the development of antiviral drugs. Here, we used a combinatorial substrate library and performed comprehensive activity profiling of SARS-CoV-2 PLpro. On the scaffold of the best hits from positional scanning, we designed optimal fluorogenic substrates and irreversible inhibitors with a high degree of selectivity for SARS PLpro. We determined crystal structures of two of these inhibitors in complex with SARS-CoV-2 PLpro that reveals their inhibitory mechanisms and provides a molecular basis for the observed substrate specificity profiles. Last, we demonstrate that SARS-CoV-2 PLpro harbors deISGylating activity similar to SARSCoV-1 PLpro but its ability to hydrolyze K48-linked Ub chains is diminished, which our sequence and structure analysis provides a basis for. Together, this work has revealed the molecular rules governing PLpro substrate specificity and provides a framework for development of inhibitors with potential therapeutic value or drug repurposing.
Assuntos
Betacoronavirus/enzimologia , Desenho de Fármacos , Inibidores de Proteases/química , Proteínas não Estruturais Virais/antagonistas & inibidores , Sequência de Aminoácidos , Betacoronavirus/isolamento & purificação , Sítios de Ligação , COVID-19 , Domínio Catalítico , Proteases 3C de Coronavírus , Infecções por Coronavirus/patologia , Infecções por Coronavirus/virologia , Cristalografia por Raios X , Cisteína Endopeptidases/genética , Cisteína Endopeptidases/metabolismo , Humanos , Cinética , Simulação de Dinâmica Molecular , Oligopeptídeos/química , Oligopeptídeos/metabolismo , Pandemias , Pneumonia Viral/patologia , Pneumonia Viral/virologia , Inibidores de Proteases/metabolismo , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , SARS-CoV-2 , Especificidade por Substrato , Ubiquitinas/metabolismo , Proteínas não Estruturais Virais/genética , Proteínas não Estruturais Virais/metabolismoRESUMO
Protein ubiquitination is a key post-translational modification regulating a wide range of biological processes. Ubiquitination involves the covalent attachment of the small protein ubiquitin to a lysine of a protein substrate. In addition to its well-established role in protein degradation, protein ubiquitination plays a role in protein-protein interactions, DNA repair, transcriptional regulation, and other cellular functions. Understanding the mechanisms and functional relevance of ubiquitin as a signaling system requires the generation of antibodies or alternative reagents that specifically detect ubiquitin in a site-specific manner. However, in contrast to other post-translational modifications such as acetylation, phosphorylation, and methylation, the instability and size of ubiquitin-76 amino acids-complicate the preparation of suitable antigens and the generation antibodies detecting such site-specific modifications. As a result, the field of ubiquitin research has limited access to specific antibodies. This severely hampers progress in understanding the regulation and function of site-specific ubiquitination in many areas of biology, specifically in epigenetics and cancer. Therefore, there is a high demand for antibodies recognizing site-specific ubiquitin modifications. Here we describe a strategy for the development of site-specific ubiquitin antibodies. Based on a recently developed antibody against site-specific ubiquitination of histone H2B, we provide detailed protocols for chemical synthesis methods for antigen preparation and discuss considerations for screening and quality control experiments.
RESUMO
In December 2019, the first cases of a novel coronavirus infection causing COVID-19 were diagnosed in Wuhan, China. Viral Papain-Like cysteine protease (PLpro, NSP3) is essential for SARS-CoV-2 replication and represents a promising target for the development of antiviral drugs. Here, we used a combinatorial substrate library containing natural and a wide variety of nonproteinogenic amino acids and performed comprehensive activity profiling of SARS-CoV-2-PLpro. On the scaffold of best hits from positional scanning we designed optimal fluorogenic substrates and irreversible inhibitors with a high degree of selectivity for SARS PLpro variants versus other proteases. We determined crystal structures of two of these inhibitors (VIR250 and VIR251) in complex with SARS-CoV-2-PLpro which reveals their inhibitory mechanisms and provides a structural basis for the observed substrate specificity profiles. Lastly, we demonstrate that SARS-CoV-2-PLpro harbors deISGylating activities similar to SARS-CoV-1-PLpro but its ability to hydrolyze K48-linked Ub chains is diminished, which our sequence and structure analysis provides a basis for. Altogether this work has revealed the molecular rules governing PLpro substrate specificity and provides a framework for development of inhibitors with potential therapeutic value or drug repositioning.
RESUMO
OTULIN (OTU Deubiquitinase With Linear Linkage Specificity) specifically hydrolyzes methionine1 (Met1)-linked ubiquitin chains conjugated by LUBAC (linear ubiquitin chain assembly complex). Here we report on the mass spectrometric identification of the OTULIN interactor SNX27 (sorting nexin 27), an adaptor of the endosomal retromer complex responsible for protein recycling to the cell surface. The C-terminal PDZ-binding motif (PDZbm) in OTULIN associates with the cargo-binding site in the PDZ domain of SNX27. By solving the structure of the OTU domain in complex with the PDZ domain, we demonstrate that a second interface contributes to the selective, high affinity interaction of OTULIN and SNX27. SNX27 does not affect OTULIN catalytic activity, OTULIN-LUBAC binding or Met1-linked ubiquitin chain homeostasis. However, via association, OTULIN antagonizes SNX27-dependent cargo loading, binding of SNX27 to the VPS26A-retromer subunit and endosome-to-plasma membrane trafficking. Thus, we define an additional, non-catalytic function of OTULIN in the regulation of SNX27-retromer assembly and recycling to the cell surface.
Assuntos
Endopeptidases/metabolismo , Endossomos/metabolismo , Nexinas de Classificação/metabolismo , Sítios de Ligação , Cristalografia por Raios X , Endopeptidases/química , Técnicas de Inativação de Genes , Transportador de Glucose Tipo 1/metabolismo , Células HEK293 , Humanos , Modelos Moleculares , Domínios PDZ , Ligação Proteica , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Transporte Proteico , Nexinas de Classificação/química , Nexinas de Classificação/genética , Ubiquitinação , Proteínas de Transporte Vesicular/metabolismoRESUMO
Ubiquitination is a process in which a protein is modified by the covalent attachment of the C-terminal carboxylic acid of ubiquitin (Ub) to the ε-amine of lysine or N-terminal methionine residue of a substrate protein or another Ub molecule. Each of the seven internal lysine residues and the N-terminal methionine residue of Ub can be linked to the C-terminus of another Ub moiety to form 8 distinct Ub linkages and the resulting differences in linkage types elicit different Ub signaling pathways. Cellular responses are triggered when proteins containing ubiquitin-binding domains (UBDs) recognize and bind to specific polyUb linkage types. To get more insight into the differences between polyUb chains, all of the seven lysine-linked di-ubiquitin molecules (diUbs) were prepared and used as a model to study their structural conformations in solution using NMR spectroscopy. We report the synthesis of diUb molecules, fully 15N-labeled on the distal (N-terminal) Ub moiety and revealed their structural orientation with respect to the proximal Ub. As expected, the diUb molecules exist in different conformations in solution, with multiple conformations known to exist for K6-, K48-, and K63-linked diUb molecules. These multiple conformations allow structural flexibility in binding with UBDs thereby inducing unique responses. One of the well-known but poorly understood UBD-Ub interaction is the recognition of K6 polyubiquitin by the ubiquitin-associated (UBA) domain of UBXN1 in the BRCA-mediated DNA repair pathway. Using our synthetic 15N-labeled diUbs, we establish here how a C-terminally extended UBA domain of UBXN1 confers specificity to K6 diUb while the non-extended version of the domain does not show any linkage preference. We show that the two distinct conformations of K6 diUb that exist in solution converge into a single conformation upon binding to this extended form of the UBA domain of the UBXN1 protein. It is likely that more of such extended UBA domains exist in nature and can contribute to linkage-specificity in Ub signaling. The isotopically labeled diUb compounds described here and the use of NMR to study their interactions with relevant partner molecules will help accelerate our understanding of Ub signaling pathways.
RESUMO
USP7 is a highly abundant deubiquitinating enzyme (DUB), involved in cellular processes including DNA damage response and apoptosis. USP7 has an unusual catalytic mechanism, where the low intrinsic activity of the catalytic domain (CD) increases when the C-terminal Ubl domains (Ubl45) fold onto the CD, allowing binding of the activating C-terminal tail near the catalytic site. Here we delineate how the target protein promotes the activation of USP7. Using NMR analysis and biochemistry we describe the order of activation steps, showing that ubiquitin binding is an instrumental step in USP7 activation. Using chemically synthesised p53-peptides we also demonstrate how the correct ubiquitinated substrate increases catalytic activity. We then used transient reaction kinetic modelling to define how the USP7 multistep mechanism is driven by target recognition. Our data show how this pleiotropic DUB can gain specificity for its cellular targets.
Assuntos
Processamento de Proteína Pós-Traducional , Peptidase 7 Específica de Ubiquitina/metabolismo , Ubiquitina/metabolismo , Isótopos de Carbono/química , Domínio Catalítico/genética , Ensaios Enzimáticos/métodos , Cinética , Modelos Químicos , Mutagênese Sítio-Dirigida , Isótopos de Nitrogênio/química , Ressonância Magnética Nuclear Biomolecular/métodos , Peptídeos/química , Peptídeos/metabolismo , Ligação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Especificidade por Substrato , Ressonância de Plasmônio de Superfície , Proteína Supressora de Tumor p53/química , Ubiquitina/química , Peptidase 7 Específica de Ubiquitina/química , Peptidase 7 Específica de Ubiquitina/genética , Peptidase 7 Específica de Ubiquitina/isolamento & purificaçãoRESUMO
Activity-based probes (ABPs) are widely used to monitor the activity of enzyme families in biological systems. Inferring enzyme activity from probe reactivity requires that the probe reacts with the enzyme at its active site; however, probe-labeling sites are rarely verified. Here we present an enhanced chemoproteomic approach to evaluate the activity and probe reactivity of deubiquitinase enzymes, using bioorthogonally tagged ABPs and a sequential on-bead digestion protocol to enhance the identification of probe-labeling sites. We confirm probe labeling of deubiquitinase catalytic Cys residues and reveal unexpected labeling of deubiquitinases on non-catalytic Cys residues and of non-deubiquitinase proteins. In doing so, we identify ZUFSP (ZUP1) as a previously unannotated deubiquitinase with high selectivity toward cleaving K63-linked chains. ZUFSP interacts with and modulates ubiquitination of the replication protein A (RPA) complex. Our reactive-site-centric chemoproteomics method is broadly applicable for identifying the reaction sites of covalent molecules, which may expand our understanding of enzymatic mechanisms.