Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 42.644
Filtrar
1.
Nat Commun ; 11(1): 4476, 2020 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-32900995

RESUMO

Mechanically stable specific heterodimerization between small protein domains have a wide scope of applications, from using as a molecular anchorage in single-molecule force spectroscopy studies of protein mechanics, to serving as force-bearing protein linker for modulation of mechanotransduction of cells, and potentially acting as a molecular crosslinker for functional materials. Here, we explore the possibility to develop heterodimerization system with a range of mechanical stability from a set of recently engineered helix-heterotetramers whose mechanical properties have yet to be characterized. We demonstrate this possibility using two randomly chosen helix-heterotetramers, showing that their mechanical properties can be modulated by changing the stretching geometry and the number of interacting helices. These helix-heterotetramers and their derivatives are sufficiently stable over physiological temperature range. Using it as mechanically stable anchorage, we demonstrate the applications in single-molecule manipulation studies of the temperature dependent unfolding and refolding of a titin immunoglobulin domain and α-actinin spectrin repeats.


Assuntos
Engenharia de Proteínas , Multimerização Proteica , Estabilidade Proteica , Actinina/química , Fenômenos Biomecânicos , Conectina/química , Modelos Moleculares , Simulação de Dinâmica Molecular , Conformação Proteica em alfa-Hélice , Domínios Proteicos , Dobramento de Proteína , Estrutura Quaternária de Proteína , Desdobramento de Proteína , Imagem Individual de Molécula , Temperatura
2.
PLoS Pathog ; 16(9): e1008871, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32936831

RESUMO

Deconvolution of syphilis pathogenesis and selection of candidate syphilis vaccinogens requires detailed knowledge of the molecular architecture of the Treponema pallidum outer membrane (OM). The T. pallidum OM contains a low density of integral OM proteins, while the spirochete's many lipoprotein immunogens are periplasmic. TP0751, a lipoprotein with a lipocalin fold, is reportedly a surface-exposed protease/adhesin and protective antigen. The rapid expansion of calycin/lipocalin structures in the RCSB PDB database prompted a comprehensive reassessment of TP0751. Small angle X-ray scattering analysis of full-length protein revealed a bipartite topology consisting of an N-terminal, intrinsically disordered region (IDR) and the previously characterized C-terminal lipocalin domain. A DALI server query using the lipocalin domain yielded 97 hits, 52 belonging to the calycin superfamily, including 15 bacterial lipocalins, but no Gram-negative surface proteins. Surprisingly, Tpp17 (TP0435) was identified as a structural ortholog of TP0751. In silico docking predicted that TP0751 can bind diverse ligands along the rim of its eight-stranded ß-barrel; high affinity binding of one predicted ligand, heme, to the lipocalin domain was demonstrated. qRT-PCR and immunoblotting revealed very low expression of TP0751 compared to other T. pallidum lipoproteins. Immunoblot analysis of immune rabbit serum failed to detect TP0751 antibodies, while only one of five patients with secondary syphilis mounted a discernible TP0751-specific antibody response. In opsonophagocytosis assays, neither TP0751 nor Tpp17 antibodies promoted uptake of T. pallidum by rabbit peritoneal macrophages. Rabbits immunized with intact, full-length TP0751 showed no protection against local or disseminated infection following intradermal challenge with T. pallidum. Our data argue that, like other lipoprotein lipocalins in dual-membrane bacteria, TP0751 is periplasmic and binds small molecules, and we propose that its IDR facilitates ligand binding by and offloading from the lipocalin domain. The inability of TP0751 to elicit opsonic or protective antibodies is consistent with a subsurface location.


Assuntos
Proteínas de Bactérias/imunologia , Vacinas Bacterianas/imunologia , Imunização , Lipoproteínas/imunologia , Sífilis/imunologia , Treponema pallidum/imunologia , Animais , Proteínas de Bactérias/genética , Vacinas Bacterianas/genética , Humanos , Lipoproteínas/genética , Domínios Proteicos , Dobramento de Proteína , Coelhos , Sífilis/genética , Sífilis/patologia , Sífilis/prevenção & controle , Treponema pallidum/genética , Treponema pallidum/patogenicidade
3.
PLoS Comput Biol ; 16(9): e1007922, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32946455

RESUMO

Prions are self-replicative protein particles lacking nucleic acids. Originally discovered for causing infectious neurodegenerative disorders, they have also been found to play several physiological roles in a variety of species. Functional and pathogenic prions share a common mechanism of replication, characterized by the ability of an amyloid conformer to propagate by inducing the conversion of its physiological, soluble counterpart. Since time-resolved biophysical experiments are currently unable to provide full reconstruction of the physico-chemical mechanisms responsible for prion replication, one must rely on computer simulations. In this work, we show that a recently developed algorithm called Self-Consistent Path Sampling (SCPS) overcomes the computational limitations of plain MD and provides a viable tool to investigate prion replication processes using state-of-the-art all-atom force fields in explicit solvent. First, we validate the reliability of SCPS simulations by characterizing the folding of a class of small proteins and comparing against the results of plain MD simulations. Next, we use SCPS to investigate the replication of the prion forming domain of HET-s, a physiological fungal prion for which high-resolution structural data are available. Our atomistic reconstruction shows remarkable similarities with a previously reported mechanism of mammalian PrPSc propagation obtained using a simpler and more approximate path sampling algorithm. Together, these results suggest that the propagation of prions generated by evolutionary distant proteins may share common features. In particular, in both these cases, prions propagate their conformation through a very similar templating mechanism.


Assuntos
Proteínas Fúngicas , Simulação de Dinâmica Molecular , Príons , Algoritmos , Biologia Computacional , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo , Príons/química , Príons/metabolismo , Conformação Proteica , Dobramento de Proteína
4.
Cell ; 182(5): 1295-1310.e20, 2020 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-32841599

RESUMO

The receptor binding domain (RBD) of the SARS-CoV-2 spike glycoprotein mediates viral attachment to ACE2 receptor and is a major determinant of host range and a dominant target of neutralizing antibodies. Here, we experimentally measure how all amino acid mutations to the RBD affect expression of folded protein and its affinity for ACE2. Most mutations are deleterious for RBD expression and ACE2 binding, and we identify constrained regions on the RBD's surface that may be desirable targets for vaccines and antibody-based therapeutics. But a substantial number of mutations are well tolerated or even enhance ACE2 binding, including at ACE2 interface residues that vary across SARS-related coronaviruses. However, we find no evidence that these ACE2-affinity-enhancing mutations have been selected in current SARS-CoV-2 pandemic isolates. We present an interactive visualization and open analysis pipeline to facilitate use of our dataset for vaccine design and functional annotation of mutations observed during viral surveillance.


Assuntos
Simulação de Acoplamento Molecular , Mutação , Peptidil Dipeptidase A/metabolismo , Glicoproteína da Espícula de Coronavírus/genética , Sítios de Ligação , Células HEK293 , Humanos , Peptidil Dipeptidase A/química , Fenótipo , Ligação Proteica , Dobramento de Proteína , Saccharomyces cerevisiae , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/metabolismo
5.
Mol Cell ; 79(5): 758-767.e6, 2020 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-32755596

RESUMO

During proteotoxic stress, bacteria maintain critical processes like DNA replication while removing misfolded proteins, which are degraded by the Lon protease. Here, we show that in Caulobacter crescentus Lon controls deoxyribonucleoside triphosphate (dNTP) pools during stress through degradation of the transcription factor CcrM. Elevated dNTP/nucleotide triphosphate (NTP) ratios in Δlon cells protects them from deletion of otherwise essential deoxythymidine triphosphate (dTTP)-producing pathways and shields them from hydroxyurea-induced loss of dNTPs. Increased dNTP production in Δlon results from higher expression of ribonucleotide reductase driven by increased CcrM. We show that misfolded proteins can stabilize CcrM by competing for limited protease and that Lon-dependent control of dNTPs improves fitness during protein misfolding conditions. We propose that linking dNTP production with availability of Lon allows Caulobacter to maintain replication capacity when misfolded protein burden increases, such as during rapid growth. Because Lon recognizes misfolded proteins regardless of the stress, this mechanism allows for response to a variety of unanticipated conditions.


Assuntos
Caulobacter crescentus/metabolismo , Nucleotídeos/metabolismo , Protease La/metabolismo , Dobramento de Proteína , Proteínas de Bactérias/metabolismo , Caulobacter crescentus/enzimologia , Elementos de DNA Transponíveis , Didesoxinucleosídeos/metabolismo , Regulação Bacteriana da Expressão Gênica , Nucleotídeo Desaminases/genética , Nucleotídeo Desaminases/metabolismo , Ribonucleotídeo Redutases/metabolismo , Estresse Fisiológico , Fatores de Transcrição/metabolismo , Regulação para Cima
6.
J Phys Chem B ; 124(38): 8201-8208, 2020 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-32790379

RESUMO

In this article, we predict the folding initiation events of the ribose phosphatase domain of protein Nsp3 and the receptor binding domain of the spike protein from the severe acute respiratory syndrome (SARS) coronavirus-2. The calculations employ the sequential collapse model and the crystal structures to identify the segments involved in the initial contact formation events of both viral proteins. The initial contact locations may provide good targets for therapeutic drug development. The proposed strategy is based on a drug binding to the contact location, thereby aiming to prevent protein folding. Peptides are suggested as a natural choice for such protein folding interdiction drugs.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/efeitos dos fármacos , Antivirais/farmacologia , Antivirais/uso terapêutico , Infecções por Coronavirus/tratamento farmacológico , Pneumonia Viral/tratamento farmacológico , Dobramento de Proteína/efeitos dos fármacos , Glicoproteína da Espícula de Coronavírus/efeitos dos fármacos , Betacoronavirus/efeitos dos fármacos , Humanos , Modelos Moleculares , Pandemias , Ligação Proteica
7.
Science ; 369(6507): 1132-1136, 2020 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-32855341

RESUMO

Naturally occurring proteins vary the precise geometries of structural elements to create distinct shapes optimal for function. We present a computational design method, loop-helix-loop unit combinatorial sampling (LUCS), that mimics nature's ability to create families of proteins with the same overall fold but precisely tunable geometries. Through near-exhaustive sampling of loop-helix-loop elements, LUCS generates highly diverse geometries encompassing those found in nature but also surpassing known structure space. Biophysical characterization showed that 17 (38%) of 45 tested LUCS designs encompassing two different structural topologies were well folded, including 16 with designed non-native geometries. Four experimentally solved structures closely matched the designs. LUCS greatly expands the designable structure space and offers a new paradigm for designing proteins with tunable geometries that may be customizable for novel functions.


Assuntos
Desenho Assistido por Computador , Engenharia de Proteínas/métodos , Dobramento de Proteína , Estrutura Secundária de Proteína
8.
Front Immunol ; 11: 1784, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32849643

RESUMO

COVID-19 has recently become the most serious threat to public health, and its prevalence has been increasing at an alarming rate. The incubation period for the virus is ~1-14 days and all age groups may be susceptible to a fatality rate of about 5.9%. COVID-19 is caused by a novel single-stranded, positive (+) sense RNA beta coronavirus. The development of a vaccine for SARS-CoV-2 is an urgent need worldwide. Immunoinformatics approaches are both cost-effective and convenient, as in silico predictions can reduce the number of experiments needed. In this study, with the aid of immunoinformatics tools, we tried to design a multi-epitope vaccine that can be used for the prevention and treatment of COVID-19. The epitopes were computed by using B cells, cytotoxic T lymphocytes (CTL), and helper T lymphocytes (HTL) base on the proteins of SARS-CoV-2. A vaccine was devised by fusing together the B cell, HTL, and CTL epitopes with linkers. To enhance the immunogenicity, the ß-defensin (45 mer) amino acid sequence, and pan-HLA DR binding epitopes (13aa) were adjoined to the N-terminal of the vaccine with the help of the EAAAK linker. To enable the intracellular delivery of the modeled vaccine, a TAT sequence (11aa) was appended to C-terminal. Linkers play vital roles in producing an extended conformation (flexibility), protein folding, and separation of functional domains, and therefore, make the protein structure more stable. The secondary and three-dimensional (3D) structure of the final vaccine was then predicted. Furthermore, the complex between the final vaccine and immune receptors (toll-like receptor-3 (TLR-3), major histocompatibility complex (MHC-I), and MHC-II) were evaluated by molecular docking. Lastly, to confirm the expression of the designed vaccine, the mRNA of the vaccine was enhanced with the aid of the Java Codon Adaptation Tool, and the secondary structure was generated from Mfold. Then we performed in silico cloning. The final vaccine requires experimental validation to determine its safety and efficacy in controlling SARS-CoV-2 infections.


Assuntos
Betacoronavirus/química , Biologia Computacional/métodos , Infecções por Coronavirus/prevenção & controle , Epitopos de Linfócito B/imunologia , Epitopos de Linfócito T/imunologia , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Proteínas Virais/imunologia , Vacinas Virais/imunologia , Sequência de Aminoácidos , Infecções por Coronavirus/virologia , Antígenos HLA-DR/imunologia , Humanos , Imunogenicidade da Vacina , Simulação de Acoplamento Molecular , Pneumonia Viral/virologia , Dobramento de Proteína , Estrutura Terciária de Proteína , Linfócitos T Citotóxicos/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Vacinas de Subunidades/imunologia , beta-Defensinas/imunologia
9.
Phys Rev Lett ; 125(6): 068102, 2020 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-32845671

RESUMO

We quantified the equilibrium (un)folding free energy ΔG_{0} of an eight-amino-acid region starting from the fully folded state of the model membrane-protein bacteriorhodopsin using single-molecule force spectroscopy. Analysis of equilibrium and nonequilibrium data yielded consistent, high-precision determinations of ΔG_{0} via multiple techniques (force-dependent kinetics, Crooks fluctuation theorem, and inverse Boltzmann analysis). We also deduced the full 1D projection of the free-energy landscape in this region. Importantly, ΔG_{0} was determined in bacteriorhodopsin's native bilayer, an advance over traditional results obtained by chemical denaturation in nonphysiological detergent micelles.


Assuntos
Bacteriorodopsinas/química , Modelos Químicos , Microscopia de Força Atômica , Dobramento de Proteína , Termodinâmica
10.
Nat Commun ; 11(1): 3797, 2020 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-32732998

RESUMO

Receptor-mediated perception of surface-exposed carbohydrates like lipo- and exo-polysaccharides (EPS) is important for non-self recognition and responses to microbial associated molecular patterns in mammals and plants. In legumes, EPS are monitored and can either block or promote symbiosis with rhizobia depending on their molecular composition. To establish a deeper understanding of receptors involved in EPS recognition, we determined the structure of the Lotus japonicus (Lotus) exopolysaccharide receptor 3 (EPR3) ectodomain. EPR3 forms a compact structure built of three putative carbohydrate-binding modules (M1, M2 and LysM3). M1 and M2 have unique ßαßß and ßαß folds that have not previously been observed in carbohydrate binding proteins, while LysM3 has a canonical ßααß fold. We demonstrate that this configuration is a structural signature for a ubiquitous class of receptors in the plant kingdom. We show that EPR3 is promiscuous, suggesting that plants can monitor complex microbial communities though this class of receptors.


Assuntos
Lipopolissacarídeos/metabolismo , Lotus/microbiologia , Lotus/fisiologia , Mesorhizobium/metabolismo , Proteínas de Plantas/metabolismo , Sequência de Aminoácidos , Mesorhizobium/genética , Fixação de Nitrogênio/fisiologia , Proteínas de Plantas/genética , Dobramento de Proteína , Nódulos Radiculares de Plantas/microbiologia , Nódulos Radiculares de Plantas/fisiologia , Simbiose/fisiologia
11.
Nat Commun ; 11(1): 4258, 2020 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-32848127

RESUMO

Protein misfolding causes a wide spectrum of human disease, and therapies that target misfolding are transforming the clinical care of cystic fibrosis. Despite this success, however, very little is known about how disease-causing mutations affect the de novo folding landscape. Here we show that inherited, disease-causing mutations located within the first nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) have distinct effects on nascent polypeptides. Two of these mutations (A455E and L558S) delay compaction of the nascent NBD1 during a critical window of synthesis. The observed folding defect is highly dependent on nascent chain length as well as its attachment to the ribosome. Moreover, restoration of the NBD1 cotranslational folding defect by second site suppressor mutations also partially restores folding of full-length CFTR. These findings demonstrate that nascent folding intermediates can play an important role in disease pathogenesis and thus provide potential targets for pharmacological correction.


Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Mutação , Substituição de Aminoácidos , Sítios de Ligação/genética , Fibrose Cística/genética , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/química , Células HEK293 , Humanos , Técnicas In Vitro , Modelos Moleculares , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Domínios Proteicos , Dobramento de Proteína , Modificação Traducional de Proteínas/genética , Estabilidade Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Ribossomos/metabolismo , Supressão Genética , Temperatura
12.
Nat Commun ; 11(1): 4254, 2020 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-32848143

RESUMO

Pulmonary fibrosis (PF) is a major public health problem with limited therapeutic options. There is a clear need to identify novel mediators of PF to develop effective therapeutics. Here we show that an ER protein disulfide isomerase, thioredoxin domain containing 5 (TXNDC5), is highly upregulated in the lung tissues from both patients with idiopathic pulmonary fibrosis and a mouse model of bleomycin (BLM)-induced PF. Global deletion of Txndc5 markedly reduces the extent of PF and preserves lung function in mice following BLM treatment. Mechanistic investigations demonstrate that TXNDC5 promotes fibrogenesis by enhancing TGFß1 signaling through direct binding with and stabilization of TGFBR1 in lung fibroblasts. Moreover, TGFß1 stimulation is shown to upregulate TXNDC5 via ER stress/ATF6-dependent transcriptional control in lung fibroblasts. Inducing fibroblast-specific deletion of Txndc5 mitigates the progression of BLM-induced PF and lung function deterioration. Targeting TXNDC5, therefore, could be a novel therapeutic approach against PF.


Assuntos
Fibrose Pulmonar Idiopática/etiologia , Fibrose Pulmonar Idiopática/metabolismo , Isomerases de Dissulfetos de Proteínas/metabolismo , Fibrose Pulmonar/etiologia , Fibrose Pulmonar/metabolismo , Receptor do Fator de Crescimento Transformador beta Tipo I/metabolismo , Tiorredoxinas/metabolismo , Fator de Crescimento Transformador beta1/metabolismo , Animais , Bleomicina/toxicidade , Modelos Animais de Doenças , Estresse do Retículo Endoplasmático , Deleção de Genes , Humanos , Fibrose Pulmonar Idiopática/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Isomerases de Dissulfetos de Proteínas/genética , Dobramento de Proteína , Estabilidade Proteica , Fibrose Pulmonar/patologia , Receptor do Fator de Crescimento Transformador beta Tipo I/química , Transdução de Sinais , Tiorredoxinas/antagonistas & inibidores , Tiorredoxinas/genética , Regulação para Cima
13.
Proc Natl Acad Sci U S A ; 117(35): 21346-21353, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32817549

RESUMO

Cells continually sample their mechanical environment using exquisite force sensors such as talin, whose folding status triggers mechanotransduction pathways by recruiting binding partners. Mechanical signals in biology change quickly over time and are often embedded in noise; however, the mechanics of force-sensing proteins have only been tested using simple force protocols, such as constant or ramped forces. Here, using our magnetic tape head tweezers design, we measure the folding dynamics of single talin proteins in response to external mechanical noise and cyclic force perturbations. Our experiments demonstrate that talin filters out external mechanical noise but detects periodic force signals over a finely tuned frequency range. Hence, talin operates as a mechanical band-pass filter, able to read and interpret frequency-dependent mechanical information through its folding dynamics. We describe our observations in the context of stochastic resonance, which we propose as a mechanism by which mechanosensing proteins could respond accurately to force signals in the naturally noisy biological environment.


Assuntos
Mecanotransdução Celular , Talina/fisiologia , Domínios Proteicos , Dobramento de Proteína , Imagem Individual de Molécula
14.
Mol Cell ; 79(5): 768-781.e7, 2020 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-32738194

RESUMO

Misfolded proteins in the endoplasmic reticulum (ER) are degraded by ER-associated degradation (ERAD). Although ERAD components involved in degradation of luminal substrates are well characterized, much less is known about quality control of membrane proteins. Here, we analyzed the degradation pathways of two short-lived ER membrane model proteins in mammalian cells. Using a CRISPR-Cas9 genome-wide library screen, we identified an ERAD branch required for quality control of a subset of membrane proteins. Using biochemical and mass spectrometry approaches, we showed that this ERAD branch is defined by an ER membrane complex consisting of the ubiquitin ligase RNF185, the ubiquitin-like domain containing proteins TMUB1/2 and TMEM259/Membralin, a poorly characterized protein. This complex cooperates with cytosolic ubiquitin ligase UBE3C and p97 ATPase in degrading their membrane substrates. Our data reveal that ERAD branches have remarkable specificity for their membrane substrates, suggesting that multiple, perhaps combinatorial, determinants are involved in substrate selection.


Assuntos
Retículo Endoplasmático/metabolismo , Proteínas de Membrana/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Sistemas CRISPR-Cas , Linhagem Celular , Sistema Enzimático do Citocromo P-450/metabolismo , Células HEK293 , Células HeLa , Humanos , Domínios Proteicos , Dobramento de Proteína , Proteólise , Proteínas de Saccharomyces cerevisiae/metabolismo , Esterol 14-Desmetilase/metabolismo
15.
Proc Natl Acad Sci U S A ; 117(33): 20292-20297, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32747529

RESUMO

Nuclear Factor of Activated T cells 5 (NFAT5) is a transcription factor (TF) that mediates protection from adverse effects of hypertonicity by increasing transcription of genes, including those that lead to cellular accumulation of protective organic osmolytes. NFAT5 has three intrinsically ordered (ID) activation domains (ADs). Using the NFAT5 N-terminal domain (NTD), which contains AD1, as a model, we demonstrate by biophysical methods that the NTD senses osmolytes and hypertonicity, resulting in stabilization of its ID regions. In the presence of sufficient NaCl or osmolytes, trehalose and sorbitol, the NFAT5 NTD undergoes a disorder-to-order shift, adopting higher average secondary and tertiary structure. Thus, NFAT5 is activated by the stress that it protects against. In its salt and/or osmolyte-induced more ordered conformation, the NTD interacts with several proteins, including HMGI-C, which is known to protect against apoptosis. These findings raise the possibility that the increased intracellular ionic strength and elevated osmolytes caused by hypertonicity activate and stabilize NFAT5.


Assuntos
Proteínas Intrinsicamente Desordenadas/química , Fatores de Transcrição/química , Escherichia coli/metabolismo , Pressão Osmótica , Ligação Proteica , Dobramento de Proteína , Cloreto de Sódio , Sorbitol , Fatores de Transcrição/metabolismo , Trealose
16.
Proc Natl Acad Sci U S A ; 117(33): 20298-20304, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32747539

RESUMO

In mammals, temperature-sensitive TRP channels make membrane conductance of cells extremely temperature dependent, allowing the detection of temperature ranging from noxious cold to noxious heat. We progressively deleted the distal carboxyl terminus domain (CTD) of the cold-activated melastatin receptor channel, TRPM8. We found that the enthalpy change associated with channel gating is proportional to the length of the CTD. Deletion of the last 36 amino acids of the CTD transforms TRPM8 into a reduced temperature-sensitivity channel (Q10 ∼4). Exposing the intracellular domain to a denaturing agent increases the energy required to open the channel indicating that cold drives channel gating by stabilizing the folded state of the CTD. Experiments in the presence of an osmoticant agent suggest that channel gating involves a change in solute-inaccessible volume in the CTD of ∼1,900 Å3 This volume matches the void space inside the coiled coil according to the cryogenic electron microscopy structure of TRPM8. The results indicate that a folding-unfolding reaction of a specialized temperature-sensitive structure is coupled to TRPM8 gating.


Assuntos
Domínios Proteicos , Dobramento de Proteína , Canais de Cátion TRPM/química , Animais , Temperatura Baixa , Microscopia Crioeletrônica , Humanos , Ativação do Canal Iônico , Modelos Moleculares , Mutagênese Sítio-Dirigida , Mutação , Oócitos , Conformação Proteica , Canais de Cátion TRPM/metabolismo , Termodinâmica , Xenopus laevis
17.
Phys Rev Lett ; 125(5): 058001, 2020 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-32794838

RESUMO

Glassy, nonexponential relaxations in globular proteins are typically attributed to conformational behaviors that are missing from intrinsically disordered proteins. Yet, we show that single molecules of a disordered-protein construct display two signatures of glassy dynamics, logarithmic relaxations and a Kovacs memory effect, in response to changes in applied tension. We attribute this to the presence of multiple independent local structures in the chain, which we corroborate with a model that correctly predicts the force dependence of the relaxation. The mechanism established here likely applies to other disordered proteins.


Assuntos
Modelos Químicos , Proteínas de Neurofilamentos/química , Cisteína/química , Cinética , Dobramento de Proteína , Termodinâmica
18.
Proc Natl Acad Sci U S A ; 117(32): 18915-18917, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32723817
19.
Proc Natl Acad Sci U S A ; 117(28): 16363-16372, 2020 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-32601205

RESUMO

The epididymal lumen contains a complex cystatin-rich nonpathological amyloid matrix with putative roles in sperm maturation and sperm protection. Given our growing understanding for the biological function of this and other functional amyloids, the problem still remains: how functional amyloids assemble including their initial transition to early oligomeric forms. To examine this, we developed a protocol for the purification of nondenatured mouse CRES, a component of the epididymal amyloid matrix, allowing us to examine its assembly to amyloid under conditions that may mimic those in vivo. Herein we use X-ray crystallography, solution-state NMR, and solid-state NMR to follow at the atomic level the assembly of the CRES amyloidogenic precursor as it progressed from monomeric folded protein to an advanced amyloid. We show the CRES monomer has a typical cystatin fold that assembles into highly branched amyloid matrices, comparable to those in vivo, by forming ß-sheet assemblies that our data suggest occur via two distinct mechanisms: a unique conformational switch of a highly flexible disulfide-anchored loop to a rigid ß-strand and by traditional cystatin domain swapping. Our results provide key insight into our understanding of functional amyloid assembly by revealing the earliest structural transitions from monomer to oligomer and by showing that some functional amyloid structures may be built by multiple and distinctive assembly mechanisms.


Assuntos
Amiloide/química , Proteínas Amiloidogênicas/química , Cistatinas/química , Amiloide/metabolismo , Amiloide/ultraestrutura , Proteínas Amiloidogênicas/metabolismo , Animais , Cristalografia por Raios X , Cistatinas/metabolismo , Epididimo/metabolismo , Espectroscopia de Ressonância Magnética , Masculino , Camundongos , Modelos Moleculares , Conformação Proteica , Dobramento de Proteína , Multimerização Proteica
20.
Mol Cell ; 79(2): 320-331.e9, 2020 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-32645369

RESUMO

Valosin-containing protein (VCP)/p97 is an AAA-ATPase that extracts polyubiquitinated substrates from multimeric macromolecular complexes and biological membranes for proteasomal degradation. During p97-mediated extraction, the substrate is largely deubiquitinated as it is threaded through the p97 central pore. How p97-extracted substrates are targeted to the proteasome with few or no ubiquitins is unknown. Here, we report that p97-extracted membrane proteins undergo a second round of ubiquitination catalyzed by the cytosolic ubiquitin ligase RNF126. RNF126 interacts with transmembrane-domain-specific chaperone BAG6, which captures p97-liberated substrates. RNF126 depletion in cells diminishes the ubiquitination of extracted membrane proteins, slows down their turnover, and dramatically stabilizes otherwise transient intermediates in the cytosol. We reconstitute the reubiquitination of a p97-extracted, misfolded multispanning membrane protein with purified factors. Our results demonstrate that p97-extracted substrates need to rapidly engage ubiquitin ligase-chaperone pairs that rebuild the ubiquitin signal for proteasome targeting to prevent harmful accumulation of unfolded intermediates.


Assuntos
Proteínas de Membrana/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Proteína com Valosina/metabolismo , Catálise , Citosol/metabolismo , Células HEK293 , Humanos , Chaperonas Moleculares/metabolismo , Dobramento de Proteína , Proteólise , Solubilidade , Ubiquitinação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA