RESUMO
Upon invading target cells, multifunctional autoprocessing repeats-in-toxin (MARTX) toxins secreted by bacterial pathogens release their disease-related modularly structured effector domains. However, it is unclear how a diverse repertoire of effector domains within these toxins are processed and activated. Here, we report that Makes caterpillars floppy-like effector (MCF)-containing MARTX toxins require ubiquitous ADP-ribosylation factor (ARF) proteins for processing and activation of intermediate effector modules, which localize in different subcellular compartments following limited processing of holo effector modules by the internal cysteine protease. Effector domains structured tandemly with MCF in intermediate modules become disengaged and fully activated by MCF, which aggressively interacts with ARF proteins present at the same location as intermediate modules and is converted allosterically into a catalytically competent protease. MCF-mediated effector processing leads ultimately to severe virulence in mice via an MCF-mediated ARF switching mechanism across subcellular compartments. This work provides insight into how bacteria take advantage of host systems to induce systemic pathogenicity.
Assuntos
Fatores de Ribosilação do ADP , ADP-Ribosilação , Toxinas Bacterianas , Vibrio vulnificus , Fatores de Ribosilação do ADP/química , Fatores de Ribosilação do ADP/metabolismo , Animais , Toxinas Bacterianas/química , Toxinas Bacterianas/metabolismo , Células HEK293 , Células HeLa , Humanos , Camundongos , Domínios Proteicos , Vibrio vulnificus/genética , Vibrio vulnificus/metabolismo , Vibrio vulnificus/patogenicidadeRESUMO
RATIONALE: SERCA2a, sarco-endoplasmic reticulum Ca2+-ATPase, is a critical determinant of cardiac function. Reduced level and activity of SERCA2a are major features of heart failure. Accordingly, intensive efforts have been made to develop efficient modalities for SERCA2a activation. We showed that the activity of SERCA2a is enhanced by post-translational modification with SUMO1 (small ubiquitin-like modifier 1). However, the roles of other post-translational modifications on SERCA2a are still unknown. OBJECTIVE: In this study, we aim to assess the role of lysine acetylation on SERCA2a function and determine whether inhibition of lysine acetylation can improve cardiac function in the setting of heart failure. METHODS AND RESULTS: The acetylation of SERCA2a was significantly increased in failing hearts of humans, mice, and pigs, which is associated with the reduced level of SIRT1 (sirtuin 1), a class III histone deacetylase. Downregulation of SIRT1 increased the SERCA2a acetylation, which in turn led to SERCA2a dysfunction and cardiac defects at baseline. In contrast, pharmacological activation of SIRT1 reduced the SERCA2a acetylation, which was accompanied by recovery of SERCA2a function and cardiac defects in failing hearts. Lysine 492 (K492) was of critical importance for the regulation of SERCA2a activity via acetylation. Acetylation at K492 significantly reduced the SERCA2a activity, presumably through interfering with the binding of ATP to SERCA2a. In failing hearts, acetylation at K492 appeared to be mediated by p300 (histone acetyltransferase p300), a histone acetyltransferase. CONCLUSIONS: These results indicate that acetylation/deacetylation at K492, which is regulated by SIRT1 and p300, is critical for the regulation of SERCA2a activity in hearts. Pharmacological activation of SIRT1 can restore SERCA2a activity through deacetylation at K492. These findings might provide a novel strategy for the treatment of heart failure.
Assuntos
Insuficiência Cardíaca/metabolismo , Miócitos Cardíacos/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Sirtuína 1/metabolismo , Acetilação , Trifosfato de Adenosina/metabolismo , Animais , Linhagem Celular , Células Cultivadas , Proteína p300 Associada a E1A/metabolismo , Insuficiência Cardíaca/enzimologia , Insuficiência Cardíaca/genética , Humanos , Lisina/genética , Lisina/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Miócitos Cardíacos/patologia , Processamento de Proteína Pós-Traducional , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/genética , Sirtuína 1/genética , SuínosRESUMO
The role of cereblon (CRBN) in T cells is not well understood. We generated mice with a deletion in Crbn and found cereblon to be an important antagonist of T-cell activation. In mice lacking CRBN, CD4(+) T cells show increased activation and IL-2 production on T-cell receptor stimulation, ultimately resulting in increased potassium flux and calcium-mediated signaling. CRBN restricts T-cell activation via epigenetic modification of Kcna3, which encodes the Kv1.3 potassium channel required for robust calcium influx in T cells. CRBN binds directly to conserved DNA elements adjacent to Kcna3 via a previously uncharacterized DNA-binding motif. Consequently, in the absence of CRBN, the expression of Kv1.3 is derepressed, resulting in increased Kv1.3 expression, potassium flux, and CD4(+) T-cell hyperactivation. In addition, experimental autoimmune encephalomyelitis in T-cell-specific Crbn-deficient mice was exacerbated by increased T-cell activation via Kv1.3. Thus, CRBN limits CD4(+) T-cell activation via epigenetic regulation of Kv1.3 expression.
Assuntos
Linfócitos T CD4-Positivos/metabolismo , Epigênese Genética , Canal de Potássio Kv1.3/genética , Ativação Linfocitária/genética , Proteínas do Tecido Nervoso/genética , Proteínas Adaptadoras de Transdução de Sinal , Animais , Linfócitos T CD4-Positivos/citologia , Cálcio/metabolismo , Células Cultivadas , Citocinas/metabolismo , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/metabolismo , Perfilação da Expressão Gênica/métodos , Canal de Potássio Kv1.3/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Proteínas do Tecido Nervoso/metabolismo , Potássio/metabolismoRESUMO
Ubiquitin-conjugating enzymes (E2) form thioester bonds with ubiquitin (Ub), which are subsequently transferred to target proteins for cellular progress. Ube2K/E2-25K (a class II E2 enzyme) contains a C-terminal ubiquitin-associated (UBA) domain that has been suggested to control ubiquitin recognition, dimerization, or poly-ubiquitin chain formation. Ube2K is a special E2 because it synthesizes K48-linked poly-ubiquitin chains without E3 ubiquitin ligase. We found that a novel interaction between the acceptor di-Ub (Ub2) and the auxiliary Ube2K promotes the discharging reaction and production of tri-Ub (Ub3), probably by guiding and positioning the K48 (in the distal Ub) of the acceptor Ub2 in the active site. We also determined the crystal structure of Ube2K-Ub2 at 2.47â¯Å resolution. Based on our structural and biochemical data, we proposed a structural model of Ub3 synthesis by Ube2K without E3.
Assuntos
Lisina/química , Enzimas Ativadoras de Ubiquitina/química , Enzimas de Conjugação de Ubiquitina/química , Ubiquitinas/química , Sítios de Ligação , Clonagem Molecular , Cristalografia por Raios X , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Humanos , Lisina/metabolismo , Simulação de Acoplamento Molecular , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Enzimas Ativadoras de Ubiquitina/genética , Enzimas Ativadoras de Ubiquitina/metabolismo , Enzimas de Conjugação de Ubiquitina/genética , Enzimas de Conjugação de Ubiquitina/metabolismo , Ubiquitinas/genética , Ubiquitinas/metabolismoRESUMO
The eukaryotic primase/polymerase complex synthesizes approximately 107 primers, one per Okazaki fragment, during the replication of mammalian chromosomes, which contain 109 base pairs. Primase catalyzes the synthesis of a short RNA segment to a single-stranded DNA template. Primase is important in DNA replication because no known replicative DNA polymerases can initiate the synthesis of a DNA strand without an initial RNA primer. The primase subcomplex is composed of a small catalytic subunit (p49), and a large accessory subunit (p58). Priming mechanisms remain poorly understood, although large numbers of structures of archaeal and eukaryotic p49 and/or p58 as well as structures of bacterial enzymes have been determined. In this study, we determined the structure of human p49â¯at 2.2â¯Å resolution with citrate in its inactive forms. Dibasic citrate was bound at the nucleotide triphosphate (NTP) ß, γ-phosphate binding site through nine hydrogen bonds. We also measured the dissociation constant of citrate and NTPs. We further demonstrated that the p49 activity is regulated by pH and citrate, which was not previously recognized as a key regulator of DNA replication. We propose that the citrate inhibits the primase and regulates DNA replication at the replication fork.
Assuntos
Ácido Cítrico/farmacologia , DNA Primase/antagonistas & inibidores , DNA Primase/química , Inibidores Enzimáticos/farmacologia , Ânions , Calorimetria , Domínio Catalítico , Ácido Cítrico/química , Cristalografia por Raios X , DNA Primase/metabolismo , Primers do DNA/metabolismo , Inibidores Enzimáticos/química , Humanos , Nucleotídeos/metabolismoRESUMO
Prompt removal of misfolded membrane proteins and misassembled membrane protein complexes is essential for membrane homeostasis. However, the elimination of these toxic proteins from the hydrophobic membrane environment has high energetic barriers. The transmembrane protein, FtsH, is the only known ATP-dependent protease responsible for this task. The mechanisms by which FtsH recognizes, unfolds, translocates, and proteolyzes its substrates remain unclear. The structure and function of the ATPase and protease domains of FtsH have been previously characterized while the role of the FtsH periplasmic domain has not clearly identified. Here, we report the 1.5-1.95 Å resolution crystal structures of the Thermotoga maritima FtsH periplasmic domain (tmPD) and describe the dynamic features of tmPD oligomerization.
Assuntos
Proteases Dependentes de ATP/química , Proteases Dependentes de ATP/ultraestrutura , Peptídeo Hidrolases/química , Peptídeo Hidrolases/ultraestrutura , Multimerização Proteica , Thermotoga maritima/enzimologia , Sítios de Ligação , Simulação por Computador , Ativação Enzimática , Modelos Químicos , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Domínios Proteicos , Relação Estrutura-AtividadeRESUMO
EF-hand domain-containing protein D2/Swiprosin-1 (EFhd2) is an actin-binding protein mainly expressed in the central nervous and the immune systems of mammals. Intracellular events linked to EFhd2, such as membrane protrusion formation, cell adhesion, and BCR signaling, are triggered by the association of EFhd2 and F-actin. We previously reported that Ca2+ enhances the F-actin-bundling ability of EFhd2 through maintaining a rigid parallel EFhd2-homodimer structure. It was also reported that the F-actin-bundling ability of EFhd2 is regulated by a phosphorylation-dependent mechanism. EGF-induced phosphorylation at Ser183 of EFhd2 has been shown to inhibit F-actin-bundling, leading to irregular actin dynamics at the leading edges of cells. However, the underlying mechanism of this inhibition has remained elusive. Here, we report the crystal structure of a phospho-mimicking mutant (S183E) of the EFhd2 core domain, where the actin-binding sites are located. Although the overall structure of the phospho-mimicking mutant is similar to the one of the unphosphorylated form, we observed a conformational transition from ordered to disordered structure in the linker region at the C-terminus of the mutant. Based on our structural and biochemical analyses, we suggest that phosphorylation at Ser183 of EFhd2 causes changes in the local conformational dynamics and the surface charge distribution of the actin-binding site, resulting in a re-coordination of the actin-binding sites in the dimer structure and a reduction of F-actin-bundling activity without affecting the F-actin-binding capacity.
Assuntos
Proteínas de Ligação ao Cálcio/química , Proteínas de Ligação ao Cálcio/metabolismo , Actinas/metabolismo , Sítios de Ligação , Proteínas de Ligação ao Cálcio/genética , Cristalografia por Raios X , Humanos , Modelos Moleculares , Mutação , Fosforilação , Conformação Proteica , Multimerização Proteica , Serina/metabolismoRESUMO
Anti-bacterial and anti-viral neuraminidase agents inhibit neuraminidase activity catalyzing the hydrolysis of terminal N-acetylneuraminic acid (Neu5Ac) from glycoconjugates and help to prevent the host pathogenesis that lead to fatal infectious diseases including influenza, bacteremia, sepsis, and cholera. Emerging antibiotic and drug resistances to commonly used anti-neuraminidase agents such as oseltamivir (Tamiflu) and zanamivir (Relenza) have highlighted the need to develop new anti-neuraminidase drugs. We obtained a serendipitous complex crystal of the catalytic domain of Clostridium perfringens neuraminidase (CpNanICD) with 2-(cyclohexylamino)ethanesulfonic acid (CHES) as a buffer. Here, we report the crystal structure of CpNanICD in complex with CHES at 1.24 Å resolution. Amphipathic CHES binds to the catalytic site of CpNanICD similar to the substrate (Neu5Ac) binding site. The 2-aminoethanesulfonic acid moiety and cyclohexyl groups of CHES interact with the cluster of three arginine residues and with the hydrophobic pocket of the CpNanICD catalytic site. In addition, a structural comparison with other bacterial and human neuraminidases suggests that CHES could serve as a scaffold for the development of new anti-neuraminidase agents targeting CpNanI.
Assuntos
Proteínas de Bactérias/química , Clostridium perfringens/química , Inibidores Enzimáticos/química , Neuraminidase/química , Taurina/análogos & derivados , Motivos de Aminoácidos , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Clonagem Molecular , Clostridium perfringens/enzimologia , Cristalografia por Raios X , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Modelos Moleculares , Neuraminidase/antagonistas & inibidores , Neuraminidase/genética , Neuraminidase/metabolismo , Domínios Proteicos , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homologia Estrutural de Proteína , Taurina/químicaRESUMO
The mitochondrial calcium uniporter (MCU) is responsible for mitochondrial calcium uptake and homeostasis. It is also a target for the regulation of cellular anti-/pro-apoptosis and necrosis by several oncogenes and tumour suppressors. Herein, we report the crystal structure of the MCU N-terminal domain (NTD) at a resolution of 1.50 Å in a novel fold and the S92A MCU mutant at 2.75 Å resolution; the residue S92 is a predicted CaMKII phosphorylation site. The assembly of the mitochondrial calcium uniporter complex (uniplex) and the interaction with the MCU regulators such as the mitochondrial calcium uptake-1 and mitochondrial calcium uptake-2 proteins (MICU1 and MICU2) are not affected by the deletion of MCU NTD. However, the expression of the S92A mutant or a NTD deletion mutant failed to restore mitochondrial Ca(2+) uptake in a stable MCU knockdown HeLa cell line and exerted dominant-negative effects in the wild-type MCU-expressing cell line. These results suggest that the NTD of MCU is essential for the modulation of MCU function, although it does not affect the uniplex formation.
Assuntos
Canais de Cálcio/química , Canais de Cálcio/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Cálcio/metabolismo , Canais de Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Cristalografia por Raios X , Células HEK293 , Células HeLa , Humanos , Mitocôndrias/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/genética , Modelos Moleculares , Mutação , Dobramento de Proteína , Domínios e Motivos de Interação entre Proteínas , Estrutura Secundária de Proteína , Estrutura Terciária de ProteínaRESUMO
RHBDL4 is an active rhomboid that specifically recognizes and cleaves atypical, positively charged transmembrane endoplasmic reticulum-associated degradation (ERAD) substrates. Interaction of valosin-containing protein (p97/VCP) and RHBDL4 is crucial to retrotranslocate polyubiquitinated substrates for ERAD pathway. Here, we report the first complex structure of VCP-binding motif (VBM) with p97 N-terminal domain (p97N) at 1.88â Å resolution. Consistent with p97 adaptor proteins including p47-ubiquitin regulatory X (UBX), gp78-VCP-interacting motif (VIM), OTU1-UBX-like element, and FAF1-UBX, RHBDL4 VBM also binds at the interface between the two lobes of p97N. Notably, the RF residues in VBM are involved in the interaction with p97N, showing a similar interaction pattern with that of FPR signature motif in the UBX domain, although the directionality is opposite. Comparison of VBM interaction with VIM of gp78, another α-helical motif that interacts with p97N, revealed that the helix direction is inversed. Nevertheless, the conserved arginine residues in both motifs participate in the majority of the interface via extensive hydrogen bonds and ionic interactions with p97N. We identified novel VBM-binding mode to p97N that involves a combination of two types of p97-cofactor specificities observed in the UBX and VIM interactions. This highlights the induced fit model of p97N interdomain cleft upon cofactor binding to form stable p97-cofactor complexes. Our mutational and biochemical analyses in defining the specific interaction between VBM and p97N have elucidated the importance of the highly conserved VBM, applicable to other VBM-containing proteins. We also showed that RHBDL4, ubiquitins, and p97 co-operate for efficient substrate dislocation.
Assuntos
Proteínas de Membrana/química , Sequência de Aminoácidos , Animais , Humanos , Conformação Proteica , Homologia de Sequência de Aminoácidos , Difração de Raios XRESUMO
A correction is made to the article by Lee et al. [(2014) Acta Cryst. D70, 1357-1365].
RESUMO
The RtcB protein has recently been identified as a 3'-phosphate RNA ligase that directly joins an RNA strand ending with a 2',3'-cyclic phosphate to the 5'-hydroxyl group of another RNA strand in a GTP/Mn(2+)-dependent reaction. Here, we report two crystal structures of Pyrococcus horikoshii RNA-splicing ligase RtcB in complex with Mn(2+) alone (RtcB/ Mn(2+)) and together with a covalently bound GMP (RtcB-GMP/Mn(2+)). The RtcB/ Mn(2+) structure (at 1.6 Å resolution) shows two Mn(2+) ions at the active site, and an array of sulfate ions nearby that indicate the binding sites of the RNA phosphate backbone. The structure of the RtcB-GMP/Mn(2+) complex (at 2.3 Å resolution) reveals the detailed geometry of guanylylation of histidine 404. The critical roles of the key residues involved in the binding of the two Mn(2+) ions, the four sulfates, and GMP are validated in extensive mutagenesis and biochemical experiments, which also provide a thorough characterization for the three steps of the RtcB ligation pathway: (i) guanylylation of the enzyme, (ii) guanylyl-transfer to the RNA substrate, and (iii) overall ligation. These results demonstrate that the enzyme's substrate-induced GTP binding site and the putative reactive RNA ends are in the vicinity of the binuclear Mn(2+) active center, which provides detailed insight into how the enzyme-bound GMP is tansferred to the 3'-phosphate of the RNA substrate for activation and subsequent nucleophilic attack by the 5'-hydroxyl of the second RNA substrate, resulting in the ligated product and release of GMP.
Assuntos
Aminoacil-tRNA Sintetases/química , Proteínas de Escherichia coli/química , Polinucleotídeo Ligases/química , Polinucleotídeo Ligases/genética , Pyrococcus horikoshii/metabolismo , Sítios de Ligação , Catálise , Domínio Catalítico , GMP Cíclico/química , Guanosina Trifosfato/química , Íons , Manganês/química , Modelos Moleculares , Conformação Molecular , Ligação Proteica , Splicing de RNA , RNA de Transferência/química , Especificidade por Substrato , Sulfatos/químicaRESUMO
Sialidase catalyzes the removal of a terminal sialic acid from glycoconjugates and plays a pivotal role in nutrition, cellular interactions and pathogenesis mediating various infectious diseases including cholera, influenza and sepsis. An array of antiviral sialidase agents have been developed and are commercially available, such as zanamivir and oseltamivir for treating influenza. However, the development of bacterial sialidase inhibitors has been much less successful. Here, natural polyphenolic geranylated flavonoids which show significant inhibitory effects against Cp-NanI, a sialidase from Clostridium perfringens, are reported. This bacterium causes various gastrointestinal diseases. The crystal structure of the Cp-NanI catalytic domain in complex with the best inhibitor, diplacone, is also presented. This structure explains how diplacone generates a stable enzyme-inhibitor complex. These results provide a structural framework for understanding the interaction between sialidase and natural flavonoids, which are promising scaffolds on which to discover new anti-sialidase agents.
Assuntos
Clostridium perfringens/enzimologia , Inibidores Enzimáticos/química , Flavonoides/química , Neuraminidase/antagonistas & inibidores , Neuraminidase/química , Domínio Catalítico , Cristalografia por Raios X , Inibidores Enzimáticos/farmacologia , Flavanonas/química , Flavanonas/farmacologia , Flavonoides/farmacologia , Concentração Inibidora 50 , Cinética , Modelos Moleculares , Conformação ProteicaRESUMO
Guanylate-kinase-associated protein (GKAP) is a scaffolding protein that links NMDA receptor-PSD-95 to Shank-Homer complexes by protein-protein interactions at the synaptic junction. GKAP family proteins are characterized by the presence of a C-terminal conserved GKAP homology domain 1 (GH1) of unknown structure and function. In this study, crystal structure of the GH1 domain of GKAP from Rattus norvegicus was determined in fusion with an N-terminal maltose-binding protein at 2.0 Å resolution. The structure of GKAP GH1 displays a three-helix bundle connected by short flexible loops. The predicted helix α4 which was not visible in the crystal structure associates weakly with the helix α3 suggesting dynamic nature of the GH1 domain. The strict conservation of GH1 domain across GKAP family members and the lack of a catalytic active site required for enzyme activity imply that the GH1 domain might serve as a protein-protein interaction module for the synaptic protein clustering.
Assuntos
Guanilato Quinases/química , Estrutura Terciária de Proteína , Sequência de Aminoácidos , Animais , Calorimetria , Modelos Moleculares , Dados de Sequência Molecular , Conformação Proteica , Ratos , Homologia de Sequência de AminoácidosRESUMO
Glycerol dehydrogenase (GDH) catalyzes glycerol oxidation to dihydroxyacetone in a NAD+-dependent manner. As an initiator of the oxidative pathway of glycerol metabolism, a variety of functional and structural studies of GDH have been conducted previously. Structural studies revealed intriguing features of GDH, like the flexible ß-hairpin and its significance. Another commonly reported structural feature is the enzyme's octameric oligomerization, though its structural details and functional significance remained unclear. Here, with a newly reported GDH structure, complexed with both NAD+ and glycerol, we analyzed the octamerization of GDH. Structural analyses revealed that octamerization reduces the structural dynamics of the N-domain, which contributes to more consistently maintaining a distance required for catalysis between the cofactor and substrate. This suggests that octamerization may play a key role in increasing the likelihood of the enzyme reaction by maintaining the ligands in an appropriate configuration for catalysis. These findings expand our understanding of the structure of GDH and its relation to the enzyme's activity.
Assuntos
NAD , Desidrogenase do Álcool de Açúcar , NAD/metabolismo , Glicerol/metabolismo , Desidrogenase do Álcool de Açúcar/metabolismo , Oxirredução , Glutamato Desidrogenase/metabolismoRESUMO
Calsequestrin (CSQ), the major intrasarcoplasmic reticulum calcium storage protein, undergoes dynamic polymerization and depolymerization in a Ca(2+)-dependent manner. However, no direct evidence of CSQ depolymerization in vivo with physiological relevance has been obtained. In the present study, live cell imaging analysis facilitated characterization of the in vivo dynamics of the macromolecular CSQ structure. CSQ2 appeared as speckles in the presence of normal sarcoplasmic reticulum (SR) Ca(2+) that were decondensed upon Ca(2+) depletion. Moreover, CSQ2 decondensation occurred only in the stoichiometric presence of junctin (JNT). When expressed alone, CSQ2 speckles remained unchanged, even after Ca(2+) depletion. FRET analysis revealed constant interactions between CSQ2 and JNT, regardless of the SR Ca(2+) concentration, implying that JNT is an essential component of the CSQ scaffold. In vitro solubility assay, electron microscopy, and atomic force microscopy studies using purified recombinant proteins confirmed Ca(2+) and JNT-dependent disassembly of the CSQ2 polymer. Accordingly, we conclude that reversible polymerization and depolymerization of CSQ are critical in SR Ca(2+) homeostasis.
Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Cálcio/metabolismo , Calsequestrina/metabolismo , Proteínas de Membrana/metabolismo , Oxigenases de Função Mista/metabolismo , Proteínas Musculares/metabolismo , Multimerização Proteica/fisiologia , Retículo Sarcoplasmático/metabolismo , Animais , Proteínas de Ligação ao Cálcio/genética , Calsequestrina/genética , Linhagem Celular , Homeostase/fisiologia , Humanos , Proteínas de Membrana/genética , Camundongos , Oxigenases de Função Mista/genética , Proteínas Musculares/genética , Retículo Sarcoplasmático/genéticaRESUMO
Proper cell division at the mid-site of gram-negative bacteria reflects critical regulation by the min system (MinC, MinD and MinE) of the cytokinetic Z ring, which is a polymer composed of FtsZ subunits. MinC and MinD act together to inhibit aberrantly positioned Z-ring formation. MinC consists of two domains: an N-terminal domain (MinCNTD), which interacts with FtsZ and inhibits FtsZ polymerization, and a C-terminal domain (MinCCTD), which interacts with MinD and inhibits the bundling of FtsZ filaments. These two domains reportedly function together, and both are essential for normal cell division. The full-length dimeric structure of MinC from Thermotoga maritima has been reported, and shows that MinC dimerization occurs via MinCCTD; MinCNTD is not involved in dimerization. Here the crystal structure of Escherichia coli MinCNTD (EcoMinCNTD) is reported. EcoMinCNTD forms a dimer via domain swapping between the first ß strands in each subunit. It is therefore suggested that the dimerization of full-length EcoMinC occurs via both MinCCTD and MinCNTD, and that the dimerized EcoMinCNTD likely plays an important role in inhibiting aberrant Z-ring localization.
Assuntos
Proteínas de Bactérias/química , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Clonagem Molecular , Cristalografia por Raios X , Dimerização , Modelos Moleculares , Dados de Sequência Molecular , Conformação Proteica , Homologia de Sequência de Aminoácidos , Thermotoga maritima/químicaRESUMO
Upc2, a zinc-cluster transcription factor, is a regulator of ergosterol biosynthesis in yeast. In response to sterol levels, the transcriptional activity of Upc2 is controlled by the C-terminal domain. In this study, the C-terminal regulatory domain of Upc2 from Saccharomyces cerevisiae was purified and crystallized by the vapour-diffusion method. To improve the diffraction quality of Upc2 crystals, a Upc2 fusion protein in which 11 residues of the variable loop (residues 715-725) were replaced by T4 lysozymes in Upc2 (Upc2-T4L) was engineered. The Upc2-T4L crystals diffracted to 2.9 Å resolution using synchrotron radiation. The crystal was trigonal, belonging to space group P3(2) with unit-cell parameters a = 67.2, b = 67.2, c = 257.5 Å. The Matthews coefficient was determined to be 3.41 Å(3) Da(-1) with two molecules in the asymmetric unit. Initial attempts to solve the structure by the single-anomalous dispersion technique using selenomethionine were successful.
Assuntos
Proteínas de Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/metabolismo , Esteróis/metabolismo , Transativadores/química , Sequência de Aminoácidos , Cristalização , Cristalografia por Raios X , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Alinhamento de Sequência , Fatores de Transcrição/químicaRESUMO
The putative lipase CpsLip from the psychrophilic bacterium Colwellia psychrerythraea 34H encodes a 34,538 Da, 308-amino-acid protein. In this study, CpsLip (UniProtKB code Q486T5) was expressed as an N-terminal hexahistidine fusion protein in Escherichia coli and purified by affinity and size-exclusion chromatography. The expression and purification of CpsLip enabled characterization of the lipase enzymatic properties of the protein. The optimal activity temperature and pH of the recombinant protein were 298 K and pH 7, respectively. CpsLip maintained over 80% activity in the low-temperature range (278-288 K), thereby suggesting that CpsLip is a cold-active lipase. Substrate-specificity analysis demonstrated that CpsLip exhibits maximum activity towards the C12 acyl group. In addition, sequence-alignment results revealed that CpsLip has a highly conserved catalytic triad in the active site consisting of residues Ser111, Asp135 and His283. Moreover, purified CpsLip was successfully crystallized using the hanging-drop vapour-diffusion method and a complete diffraction data set was collected to 4.0 Å resolution using synchrotron radiation on the BL-5A beamline of the Photon Factory.
Assuntos
Alteromonadaceae/enzimologia , Proteínas de Bactérias/química , Temperatura Baixa , Lipase/química , Alteromonadaceae/genética , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Lipase/genética , Lipase/isolamento & purificação , Metaloendopeptidases , Dados de Sequência Molecular , Difração de Raios XRESUMO
The dynamin-like GTPase atlastin is believed to be the minimal machinery required for homotypic endoplasmic reticulum (ER) membrane fusion, mainly because Drosophila atlastin is sufficient to drive liposome fusion. However, it remains unclear whether mammalian atlastins, including the three human atlastins, are sufficient to induce liposome fusion, raising doubts about their major roles in mammalian cells. Here, we show that all human atlastins are sufficient to induce fusion when reconstituted into liposomes with a lipid composition mimicking that of the ER. Although the fusogenic activity of ATL1, which is predominantly expressed in neuronal cells, was weaker than that of ATL2 or ATL3, the addition of M1-spastin, a neuron-specific factor, markedly increased ATL1-mediated liposome fusion. Although we observed efficient fusion between ER microsomes isolated from cultured, non-neuronal cells that predominantly express ATL2-1, an autoinhibited isoform of ATL2, ATL2-1 failed to support liposome fusion by itself as reported previously, indicating that cellular factors enable ATL2-1 to mediate ER fusion in vivo.