RESUMO
BACKGROUND: The human eosinophil Charcot-Leyden crystal (CLC) protein is a member of the Galectin superfamily and is also known as galectin-10 (Gal-10). CLC/Gal-10 forms the distinctive hexagonal bipyramidal crystals that are considered hallmarks of eosinophil participation in allergic responses and related inflammatory reactions; however, the glycan-containing ligands of CLC/Gal-10, its cellular function(s), and its role(s) in allergic diseases are unknown. OBJECTIVE: We sought to determine the binding partners of CLC/Gal-10 and elucidate its role in eosinophil biology. METHODS: Intracellular binding partners were determined by ligand blotting with CLC/Gal-10, followed by coimmunoprecipitation and coaffinity purifications. The role of CLC/Gal-10 in eosinophil function was determined by using enzyme activity assays, confocal microscopy, and short hairpin RNA knockout of CLC/Gal-10 expression in human CD34+ cord blood hematopoietic progenitors differentiated to eosinophils. RESULTS: CLC/Gal-10 interacts with both human eosinophil granule cationic ribonucleases (RNases), namely, eosinophil-derived neurotoxin (RNS2) and eosinophil cationic protein (RNS3), and with murine eosinophil-associated RNases. The interaction is independent of glycosylation and is not inhibitory toward endoRNase activity. Activation of eosinophils with INF-γ induces the rapid colocalization of CLC/Gal-10 with eosinophil-derived neurotoxin/RNS2 and CD63. Short hairpin RNA knockdown of CLC/Gal-10 in human cord blood-derived CD34+ progenitor cells impairs eosinophil granulogenesis. CONCLUSIONS: CLC/Gal-10 functions as a carrier for the sequestration and vesicular transport of the potent eosinophil granule cationic RNases during both differentiation and degranulation, enabling their intracellular packaging and extracellular functions in allergic inflammation.
Assuntos
Grânulos Citoplasmáticos/metabolismo , Proteína Catiônica de Eosinófilo/metabolismo , Neurotoxina Derivada de Eosinófilo/metabolismo , Eosinófilos/imunologia , Glicoproteínas/metabolismo , Granuloma/metabolismo , Células-Tronco Hematopoéticas/fisiologia , Hipersensibilidade/metabolismo , Lisofosfolipase/metabolismo , Animais , Antígenos CD34/metabolismo , Células Cultivadas , Galectinas/metabolismo , Humanos , Camundongos , Ligação ProteicaRESUMO
Mammalian members of glycosyltransferase family 6 (GT6) of the CAZy database have a GT-A fold containing a conserved Asp-X-Asp (DXD) sequence that binds an essential metal cofactor. Bacteroides ovatus GT6a represents a GT6 clade found in more than 30 Gram-negative bacteria that is similar in sequence to the catalytic domains of mammalian GT6, but has an Asn(95)-Ala-Asn(97) (NXN) sequence substituted for the DXD motif and metal-independent catalytic activity. Co-crystals of a low activity mutant of BoGT6a (E192Q) with UDP-GalNAc contained protein complexes with intact UDP-GalNAc and two forms with hydrolysis products (UDP plus GalNAc) representing an initial closed complex and later open form primed for product release. Two cationic residues near the C terminus of BoGT6a, Lys(231) and Arg(243), interact with the diphosphate moiety of UDP-GalNAc, but only Lys(231) interacts with the UDP product and may function in leaving group stabilization. The amide group of Asn(95), the first Asn of the NXN motif, interacts with the ribose moiety of the substrate. This metal-independent GT6 resembles its metal-dependent homologs in undergoing conformational changes on binding UDP-GalNAc that arise from structuring the C terminus to cover this substrate. It appears that in the GT6 family, the metal cofactor functions specifically in binding the UDP moiety in the donor substrate and transition state, actions that can be efficiently performed by components of the polypeptide chain.
Assuntos
Bacteroides/enzimologia , Glicosiltransferases/química , Glicosiltransferases/metabolismo , Uridina Difosfato N-Acetilgalactosamina/metabolismo , Bacteroides/química , Bacteroides/metabolismo , Cristalografia por Raios X , Hidrólise , Metais/metabolismo , Modelos Moleculares , Conformação Proteica , Uridina Difosfato N-Acetilgalactosamina/químicaRESUMO
Clostridium difficile is a major problem as an aetiological agent for antibiotic-associated diarrhoea. The mechanism by which the bacterium colonizes the gut during infection is poorly understood, but undoubtedly involves a myriad of components present on the bacterial surface. The mechanism of C. difficile surface-layer (S-layer) biogenesis is also largely unknown but involves the post-translational cleavage of a single polypeptide (surface-layer protein A; SlpA) into low- and high-molecular-weight subunits by Cwp84, a surface-located cysteine protease. Here, the first crystal structure of the surface protein Cwp84 is described at 1.4â Å resolution and the key structural components are identified. The truncated Cwp84 active-site mutant (amino-acid residues 33-497; C116A) exhibits three regions: a cleavable propeptide and a cysteine protease domain which exhibits a cathepsin L-like fold followed by a newly identified putative carbohydrate-binding domain with a bound calcium ion, which is referred to here as a lectin-like domain. This study thus provides the first structural insights into Cwp84 and a strong base to elucidate its role in the C. difficile S-layer maturation mechanism.
Assuntos
Clostridioides difficile/química , Cisteína Endopeptidases/química , Cisteína Proteases/química , Lectinas/química , Sequência de Aminoácidos , Primers do DNA , Dados de Sequência Molecular , Conformação Proteica , Homologia de Sequência de AminoácidosRESUMO
Cwp19 is a putatively surface-located protein from Clostridium difficile. A recombinant N-terminal protein (residues 27-401) lacking the signal peptide and the C-terminal cell-wall-binding repeats (PFam04122) was crystallized using the sitting-drop vapour-diffusion method and diffracted to 2â Å resolution. The crystal appeared to belong to the primitive monoclinic space group P2(1), with unit-cell parameters a=109.1, b=61.2, c=109.2â Å, ß=111.85°, and is estimated to contain two molecules of Cwp19 per asymmetric unit.
Assuntos
Proteínas de Bactérias/química , Clostridioides difficile/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Parede Celular/química , Cristalização , Cristalografia por Raios X , Expressão GênicaRESUMO
Carbonic anhydrase (CA) catalyzes the reversible hydration of carbon dioxide to hydrogen carbonate, and its role in maintaining pH balance has made it an attractive drug target. Steroidal sulfamate esters, inhibitors of the cancer drug target steroid sulfatase (STS), are sequestered in vivo by CA II in red blood cells, which may be the origin of their excellent drug properties. Understanding the structural basis of this is important for drug design. Structures of CA II complexed with 2-methoxyestradiol 3-O-sulfamate (3), 2-ethylestradiol 3,17-O,O-bis(sulfamate) (4), and 2-methoxyestradiol 17-O-sulfamate (5) are reported to 2.10, 1.85, and 1.64 A, respectively. Inhibitor 3 interacts with the active site Zn(II) ion through the 3-O-sulfamate, while inhibitors 4 and 5 bind through their 17-O-sulfamate. Comparison of the IC(50) values for CA II inhibition gave respective values of 56, 662, 2113, 169, 770, and 86 nM for estrone 3-O-sulfamate (1), 2-methoxyestradiol 3,17-O,O-bis(sulfamate) (2), 3, 4, 5, and 5'-((4H-1,2,4-triazol-4-yl)methyl)-3-chloro-2'-cyanobiphenyl-4-yl sulfamate (6), a nonsteroidal dual aromatase-sulfatase inhibitor. Inhibitors 2, 5, and 6 showed binding to a second adjacent site that is capable of binding both steroidal and nonsteroidal ligands. Examination of both IC(50) values and crystal structures suggests that 2-substituents on the steroid nucleus hinder binding via a 3-O-sulfamate, leading to coordination through a 17-O-sulfamate if present. These results underline the influence of small structural changes on affinity and mode of binding, the degree of flexibility in the design of sulfamate-based inhibitors, and suggest a strategy for inhibitors which interact with both the active site and the second adjacent binding site simultaneously that could be both potent and selective.
Assuntos
Anidrase Carbônica II/química , Bicarbonatos/metabolismo , Sítios de Ligação , Dióxido de Carbono/metabolismo , Anidrase Carbônica II/antagonistas & inibidores , Colorimetria , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Estrona/análogos & derivados , Estrona/química , Estrona/farmacologia , Humanos , Cinética , Modelos Moleculares , Conformação ProteicaRESUMO
The specificities of glycosyltransferases make them useful for the synthesis of biologically active oligosaccharides, but also restrict their range of products. In substrate engineering, substrate promiscuity is enhanced by attaching removable interactive groups to weak substrates. Thus, the attachment of betap-nitrophenyl converts galactose from a poor into a good substrate of alpha-1,3-galactosyltransferase. The crystallographic structure of a complex of alpha3GT containing p-nitrophenyl-beta-galactoside shows that the p-nitrophenyl binds similarly to the N-acetylglucosamine of the substrate, N-acetyllactosamine, interacting with the indole of Trp249. p-Nitrophenyl, unlike N-acetylglucosamine, makes no H-bonds but has more non-polar interactions, making it an effective monosaccharide mimetic.
Assuntos
Galactosiltransferases/química , Nitrofenilgalactosídeos/química , Cristalografia por Raios X , Galactosiltransferases/genética , Conformação ProteicaRESUMO
Thymidine phosphorylase (TP) first identified as platelet derived endothelial cell growth factor (PD-ECGF) plays a key role in nucleoside metabolism. Human TP (hTP) is implicated in angiogenesis and is overexpressed in several solid tumors. Here, we report the crystal structures of recombinant hTP and its complex with a substrate 5-iodouracil (5IUR) at 3.0 and 2.5A, respectively. In addition, we provide information on the role of specific residues in the enzymatic activity of hTP through mutagenesis and kinetic studies.
Assuntos
Timidina Fosforilase/química , Uracila/análogos & derivados , Cristalografia por Raios X , Humanos , Mutação , Fosfatos/química , Conformação Proteica , Timidina Fosforilase/genética , Uracila/químicaRESUMO
Botulinum neurotoxins (BoNTs) modulate cholinergic nerve terminals to result in neurotransmitter blockade. BoNTs consists of catalytic (LC), translocation (Hn) and cell-binding domains (Hc). The binding function of the Hc domain is essential for BoNTs to bind the neuronal cell membrane, therefore, removal of the Hc domain results in a product that retains the endopeptidase activity of the LC but is non-toxic. Thus, a molecule consisting of LC and Hn domains of BoNTs, termed LHn, is a suitable molecule for engineering novel therapeutics. The structure of LHA at 2.6 A reported here provides an understanding of the structural implications and challenges of engineering therapeutic molecules that combine functional properties of LHn of BoNTs with specific ligand partners to target different cell types.
Assuntos
Toxinas Botulínicas Tipo A/química , Colinérgicos/química , Endopeptidases/química , Toxinas Botulínicas Tipo A/genética , Toxinas Botulínicas Tipo A/toxicidade , Catálise , Colinérgicos/toxicidade , Cristalografia por Raios X , Endopeptidases/genética , Endopeptidases/toxicidade , Engenharia de Proteínas , Estabilidade Proteica , Estrutura Terciária de Proteína , Transporte Proteico , Proteína 25 Associada a Sinaptossoma/químicaRESUMO
alpha-1,3-Galactosyltransferase (alpha3GT) catalyzes the transfer of galactose from UDP-galactose to form an alpha 1-3 link with beta-linked galactosides; it is part of a family of homologous retaining glycosyltransferases that includes the histo-blood group A and B glycosyltransferases, Forssman glycolipid synthase, iGb3 synthase, and some uncharacterized prokaryotic glycosyltransferases. In mammals, the presence or absence of active forms of these enzymes results in antigenic differences between individuals and species that modulate the interplay between the immune system and pathogens. The catalytic mechanism of alpha3GT is controversial, but the structure of an enzyme complex with the donor substrate could illuminate both this and the basis of donor substrate specificity. We report here the structure of the complex of a low-activity mutant alpha3GT with UDP-galactose (UDP-gal) exhibiting a bent configuration stabilized by interactions of the galactose with multiple residues in the enzyme including those in a highly conserved region (His315 to Ser318). Analysis of the properties of mutants containing substitutions for these residues shows that catalytic activity is strongly affected by His315 and Asp316. The negative charge of Asp316 is crucial for catalytic activity, and structural studies of two mutants show that its interaction with Arg202 is needed for an active site structure that facilitates the binding of UDP-gal in a catalytically competent conformation.
Assuntos
Ácido Aspártico/química , Galactosiltransferases/metabolismo , Uridina Difosfato Galactose/química , Uridina Difosfato Galactose/metabolismo , Animais , Sítios de Ligação , Bovinos , Cristalografia por Raios X , Galactosiltransferases/química , Galactosiltransferases/genética , Modelos Moleculares , Mutação , Conformação Proteica , Relação Estrutura-Atividade , Especificidade por SubstratoRESUMO
Complex glycans have important roles in biological recognition processes and considerable pharmaceutical potential. The synthesis of novel glycans can be facilitated by engineering glycosyltransferases to modify their substrate specificities. The choice of sites to modify requires the knowledge of the structures of enzyme-substrate complexes while the complexity of protein structures necessitates the exploration of a large array of multisite mutations. The retaining glycosyltransferase, alpha-1,3-galactosyltransferase (alpha3GT), which catalyzes the synthesis of the alpha-Gal epitope, has strict specificity for UDP-galactose as a donor substrate. Based on the structure of a complex of UDP-galactose with alpha3GT, the specificity for the galactose moiety can be partly attributed to residues that interact with the galactose 2-OH group, particularly His280 and Ala282. With the goal of engineering a variant of bovine alpha3GT with GalNAc transferase activity, we constructed a limited library of 456 alpha3GT mutants containing 19 alternative amino acids at position 280, two each at 281 and 282 and six at position 283. Clones (1500) were screened by assaying partially purified bacterially expressed variants for GalNAc transferase activity. Mutants with the highest levels of GalNAc transferase activity, AGGL or GGGL, had substitutions at all four sites. The AGGL mutant had slightly superior GalNAc transferase activity amounting to about 3% of the activity of the wild-type enzyme with UDP-Gal. This mutant had a low activity with UDP-Gal; its crystallographic structure suggests that the smaller side chains at residues 280-282 form a pocket to accommodate the larger acetamido group of GalNAc. Mutational studies indicate that Leu283 is important for stability in this mutant.
Assuntos
Galactosiltransferases/genética , Uridina Difosfato Galactose/química , Cristalografia por Raios X , Biblioteca Gênica , Cinética , Leucina/genética , Leucina/metabolismo , Modelos Moleculares , Mutação , Polissacarídeos/biossíntese , Conformação Proteica , Uridina Difosfato Galactose/genéticaRESUMO
Receptor tyrosine kinase FGFR3 is involved in many signaling networks and is frequently mutated in developmental disorders and cancer. The Hsp90/Cdc37 chaperone system is essential for function of normal and neoplastic cells. Here we uncover the mechanistic inter-relationships between these proteins by combining approaches including NMR, HDX-MS, and SAXS. We show that several disease-linked mutations convert FGFR3 to a stronger client, where the determinant underpinning client strength involves an allosteric network through the N-lobe and at the lobe interface. We determine the architecture of the client kinase/Cdc37 complex and demonstrate, together with site-specific information, that binding of Cdc37 to unrelated kinases induces a common, extensive conformational remodeling of the kinase N-lobe, beyond localized changes and interactions within the binary complex. As further shown for FGFR3, this processing by Cdc37 deactivates the kinase and presents it, in a specific orientation established in the complex, for direct recognition by Hsp90.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Chaperoninas/metabolismo , Proteínas de Choque Térmico HSP90/metabolismo , Mutação , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/química , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/metabolismo , Sítio Alostérico , Humanos , Modelos Moleculares , Ressonância Magnética Nuclear Biomolecular , Ligação Proteica , Conformação Proteica , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/genética , Espalhamento a Baixo Ângulo , Difração de Raios XRESUMO
Mutations in Angiogenin (ANG), a member of the Ribonuclease A superfamily (also known as RNase 5) are known to be associated with Amyotrophic Lateral Sclerosis (ALS, motor neurone disease) (sporadic and familial) and Parkinson's Disease (PD). In our previous studies we have shown that ANG is expressed in neurons during neuro-ectodermal differentiation, and that it has both neurotrophic and neuroprotective functions. In addition, in an extensive study on selective ANG-ALS variants we correlated the structural changes to the effects on neuronal survival and the ability to induce stress granules in neuronal cell lines. Furthermore, we have established that ANG-ALS variants which affect the structure of the catalytic site and either decrease or increase the RNase activity affect neuronal survival. Neuronal cell lines expressing the ANG-ALS variants also lack the ability to form stress granules. Here, we report a detailed experimental structural study on eleven new ANG-PD/ALS variants which will have implications in understanding the molecular basis underlying their role in PD and ALS.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Variação Genética , Mutação , Doença de Parkinson/metabolismo , Ribonuclease Pancreático/química , Ribonuclease Pancreático/metabolismo , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/patologia , Cristalografia por Raios X , Humanos , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Doença de Parkinson/genética , Doença de Parkinson/patologia , Conformação Proteica , Ribonuclease Pancreático/genéticaRESUMO
Protein kinases share significant structural similarity; however, structural features alone are insufficient to explain their diverse functions. Thus, bridging the gap between static structure and function requires a more detailed understanding of their dynamic properties. For example, kinase activation may occur via a switch-like mechanism or by shifting a dynamic equilibrium between inactive and active states. Here, we utilize a combination of FRET and molecular dynamics (MD) simulations to probe the activation mechanism of the kinase domain of Fibroblast Growth Factor Receptor (FGFR). Using genetically-encoded, site-specific incorporation of unnatural amino acids in regions essential for activation, followed by specific labeling with fluorescent moieties, we generated a novel class of FRET-based reporter to monitor conformational differences corresponding to states sampled by non phosphorylated/inactive and phosphorylated/active forms of the kinase. Single molecule FRET analysis in vitro, combined with MD simulations, shows that for FGFR kinase, there are populations of inactive and active states separated by a high free energy barrier resulting in switch-like activation. Compared to recent studies, these findings support diversity in features of kinases that impact on their activation mechanisms. The properties of these FRET-based constructs will also allow further studies of kinase dynamics as well as applications in vivo.
Assuntos
Transferência Ressonante de Energia de Fluorescência/métodos , Simulação de Dinâmica Molecular , Receptor Tipo 1 de Fator de Crescimento de Fibroblastos/química , Imagem Individual de Molécula/métodos , Substituição de Aminoácidos , Humanos , Fosforilação , Domínios Proteicos , Processamento de Proteína Pós-Traducional , Receptor Tipo 1 de Fator de Crescimento de Fibroblastos/genética , Receptor Tipo 1 de Fator de Crescimento de Fibroblastos/metabolismoRESUMO
Frequent genetic alterations discovered in FGFRs and evidence implicating some as drivers in diverse tumors has been accompanied by rapid progress in targeting FGFRs for anticancer treatments. Wider assessment of the impact of genetic changes on the activation state and drug responses is needed to better link the genomic data and treatment options. We here apply a direct comparative and comprehensive analysis of FGFR3 kinase domain variants representing the diversity of point-mutations reported in this domain. We reinforce the importance of N540K and K650E and establish that not all highly activating mutations (for example R669G) occur at high-frequency and conversely, that some "hotspots" may not be linked to activation. Further structural characterization consolidates a mechanistic view of FGFR kinase activation and extends insights into drug binding. Importantly, using several inhibitors of particular clinical interest (AZD4547, BGJ-398, TKI258, JNJ42756493 and AP24534), we find that some activating mutations (including different replacements of the same residue) result in distinct changes in their efficacy. Considering that there is no approved inhibitor for anticancer treatments based on FGFR-targeting, this information will be immediately translatable to ongoing clinical trials.
Assuntos
Benzamidas/farmacologia , Biomarcadores Tumorais/genética , Transformação Celular Neoplásica/patologia , Mutação , Neoplasias/genética , Piperazinas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Pirazóis/farmacologia , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/genética , Animais , Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Transformação Celular Neoplásica/efeitos dos fármacos , Transformação Celular Neoplásica/genética , Humanos , Camundongos , Células NIH 3T3 , Neoplasias/tratamento farmacológico , Neoplasias/patologia , Fosforilação/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacosRESUMO
2'-Fluoro-2'-deoxyuridine 3'-phosphate (dU(F)MP) and arabinouridine 3'-phosphate (araUMP) have non-natural furanose rings. dU(F)MP and araUMP were prepared by chemical synthesis and found to have three- to sevenfold higher affinity than uridine 3'-phosphate (3'-UMP) or 2'-deoxyuridine 3'-phosphate (dUMP) for ribonuclease A (RNase A). These differences probably arise (in part) from the phosphoryl groups of 3'-UMP, dU(F)MP, and araUMP (pK(a) = 5.9) being more anionic than that of dUMP (pK(a) = 6.3). The three-dimensional structures of the crystalline complexes of RNase A with dUMP, dU(F)MP and araUMP were determined at < 1.7 A resolution by X-ray diffraction analysis. In these three structures, the uracil nucleobases and phosphoryl groups bind to the enzyme in a nearly identical position. Unlike 3'-UMP and dU(F)MP, dUMP and araUMP bind with their furanose rings in the preferred pucker. In the RNase A.araUMP complex, the 2'-hydroxyl group is exposed to the solvent. All four 3'-nucleotides bind more tightly to wild-type RNase A than to its T45G variant, which lacks the residue that interacts most closely with the uracil nucleobase. These findings illuminate in atomic detail the interaction of RNase A and 3'-nucleotides, and indicate that non-natural furanose rings can serve as the basis for more potent inhibitors of catalysis by RNase A.
Assuntos
Nucleotídeos/metabolismo , Cristalografia por Raios X , Modelos Moleculares , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Nucleotídeos/química , Ligação Proteica , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
Fibroblast growth factor receptors (FGFRs) are recognized therapeutic targets in cancer. We here describe insights underpinning the impact of mutations on FGFR1 and FGFR3 kinase activity and drug efficacy, using a combination of computational calculations and experimental approaches including cellular studies, X-ray crystallography and biophysical and biochemical measurements. Our findings reveal that some of the tested compounds, in particular TKI258, could provide therapeutic opportunity not only for patients with primary alterations in FGFR but also for acquired resistance due to the gatekeeper mutation. The accuracy of the computational methodologies applied here shows a potential for their wider application in studies of drug binding and in assessments of functional and mechanistic impacts of mutations, thus assisting efforts in precision medicine.
RESUMO
Human angiogenin (ANG) is an angiogenic molecule and a ribonucleolytic enzyme with significant amino acid sequence identity to pancreatic RNase A, plays a critical role in the establishment and growth of tumours. An association between ANG and cancer has been observed in more than 25 clinical studies to date. In addition, ANG has now been shown to be implicated in Amyotrophic Lateral Sclerosis (ALS) and Parkinson's Disease (PD). Structural and biochemical studies so far have showed several distinguishing features of ANG molecule compared to RNase A and provided details of the putative cell binding site, active site, nuclear translocation sequence and the roles of residues in binding and cleaving RNA. A key finding elucidated from the structural study on ANG is the presence of a 'blocked' C-terminus (part of the active site apparatus) compared with RNase A. Here we report the crystal structure of ANG with an 'engineered-loop' from eosinophil derived neurotoxin (a homologue of ANG) which has resulted with local perturbations (conformational flexibility) at the cell binding site and at the C-terminus of the molecule. This experimental observation will now provide a new avenue to design compounds (potent inhibitors) through a structure guided drug design route.
RESUMO
Mutations in angiogenin (ANG), a member of the ribonuclease A superfamily, are associated with amyotrophic lateral sclerosis (ALS; sporadic and familial) and Parkinson's disease. We have previously shown that ANG is expressed in neurons during neuro-ectodermal differentiation, and that it has both neurotrophic and neuroprotective functions. Here we report the atomic resolution structure of native ANG and 11 ANG-ALS variants. We correlate the structural changes to the effects on neuronal survival and the ability to induce stress granules in neuronal cell lines. ANG-ALS variants that affect the structure of the catalytic site and either decrease or increase the RNase activity affect neuronal survival. Neuronal cell lines expressing the ANG-ALS variants also lack the ability to form stress granules. Our structure-function studies on these ANG-ALS variants are the first to provide insights into the cellular and molecular mechanisms underlying their role in ALS.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Grânulos Citoplasmáticos/metabolismo , Neurônios/metabolismo , Ribonuclease Pancreático/química , Ribonuclease Pancreático/metabolismo , Esclerose Lateral Amiotrófica/genética , Animais , Linhagem Celular , Linhagem Celular Tumoral , Cristalografia por Raios X , Humanos , Imuno-Histoquímica , Camundongos , Mutação , Ribonuclease Pancreático/genéticaRESUMO
Snakebites are a major neglected tropical disease responsible for as many as 95000 deaths every year worldwide. Viper venom serine proteases disrupt haemostasis of prey and victims by affecting various stages of the blood coagulation system. A better understanding of their sequence, structure, function and phylogenetic relationships will improve the knowledge on the pathological conditions and aid in the development of novel therapeutics for treating snakebites. A large dataset for all available viper venom serine proteases was developed and analysed to study various features of these enzymes. Despite the large number of venom serine protease sequences available, only a small proportion of these have been functionally characterised. Although, they share some of the common features such as a C-terminal extension, GWG motif and disulphide linkages, they vary widely between each other in features such as isoelectric points, potential N-glycosylation sites and functional characteristics. Some of the serine proteases contain substitutions for one or more of the critical residues in catalytic triad or primary specificity pockets. Phylogenetic analysis clustered all the sequences in three major groups. The sequences with substitutions in catalytic triad or specificity pocket clustered together in separate groups. Our study provides the most complete information on viper venom serine proteases to date and improves the current knowledge on the sequence, structure, function and phylogenetic relationships of these enzymes. This collective analysis of venom serine proteases will help in understanding the complexity of envenomation and potential therapeutic avenues.
RESUMO
Histo-blood group antigens (HBGAs) are a source of antigenic variation between individuals that modulates resistance and susceptibility to pathogens and is a barrier to the spread of enveloped viruses. HBGAs are also produced by a few prokaryotes where they are synthesized by glycosyltransferases (GTs) related to human HBGA synthases. Here we report the first structure of a bacterial GT of this family, from an intestinal resident, Bacteroides ovatus. Unlike its mammalian homologues and other GTs with similar folds, this protein lacks a metal-binding Asp-X-Asp motif and is fully active in the absence of divalent metal ions, yet is strikingly similar in structure and in its interactions with substrates to structurally characterized mammalian metal-dependent mammalian homologues. This shows how an apparently major divergence in catalytic properties can be accommodated by minor structural adjustments and illustrates the structural underpinnings of horizontal transfer of a functional gene from prokaryotes to vertebrates.