RESUMO
The nervous system is composed of a variety of neurons and glial cells with different morphology and functions. In the mammalian peripheral nervous system (PNS) or the lower vertebrate central nervous system (CNS), most neurons can regenerate extensively after axotomy, while the neurons in the mammalian CNS possess only limited regenerative ability. This heterogeneity is common within and across species. The studies about the transcriptomes after nerve injury in different animal models have revealed a series of molecular and cellular events that occurred in neurons after axotomy. However, responses of various types of neurons located in different positions of individuals were different remarkably. Thus, researchers aim to find the key factors that are conducive to regeneration, so as to provide the molecular basis for solving the regeneration difficulties after CNS injury. Here we review the heterogeneity of axonal regeneration among different cell subtypes in different animal models or the same organ, emphasizing the importance of comparative studies within and across species.
Assuntos
Axônios , Regeneração Nervosa , Animais , Regeneração Nervosa/fisiologia , Axotomia , Sistema Nervoso Periférico , Sistema Nervoso Central , MamíferosRESUMO
The coordination of carbon and nitrogen metabolism is essential for bacteria to adapt to nutritional variations in the environment, but the underlying mechanism remains poorly understood. In autotrophic cyanobacteria, high CO2 levels favor the carboxylase activity of ribulose 1,5 bisphosphate carboxylase/oxygenase (RuBisCO) to produce 3-phosphoglycerate, whereas low CO2 levels promote the oxygenase activity of RuBisCO, leading to 2-phosphoglycolate (2-PG) production. Thus, the 2-PG level is reversely correlated with that of 2-oxoglutarate (2-OG), which accumulates under a high carbon/nitrogen ratio and acts as a nitrogen-starvation signal. The LysR-type transcriptional repressor NAD(P)H dehydrogenase regulator (NdhR) controls the expression of genes related to carbon metabolism. Based on genetic and biochemical studies, we report here that 2-PG is an inducer of NdhR, while 2-OG is a corepressor, as found previously. Furthermore, structural analyses indicate that binding of 2-OG at the interface between the two regulatory domains (RD) allows the NdhR tetramer to adopt a repressor conformation, whereas 2-PG binding to an intradomain cleft of each RD triggers drastic conformational changes leading to the dissociation of NdhR from its target DNA. We further confirmed the effect of 2-PG or 2-OG levels on the transcription of the NdhR regulon. Together with previous findings, we propose that NdhR can sense 2-OG from the Krebs cycle and 2-PG from photorespiration, two key metabolites that function together as indicators of intracellular carbon/nitrogen status, thus representing a fine sensor for the coordination of carbon and nitrogen metabolism in cyanobacteria.
Assuntos
Carbono/metabolismo , Cianobactérias/metabolismo , Genes Reguladores , NAD(P)H Desidrogenase (Quinona)/metabolismo , Nitrogênio/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Dióxido de Carbono/metabolismo , Cianobactérias/genética , Regulação Bacteriana da Expressão Gênica , Glicolatos/metabolismo , Ácidos Cetoglutáricos/metabolismo , NAD(P)H Desidrogenase (Quinona)/genética , Ribulose-Bifosfato Carboxilase/genética , Ribulose-Bifosfato Carboxilase/metabolismo , Transdução de SinaisRESUMO
BACKGROUND: Rice is an important food crop in China. Seed drying is an important step in the production of rice seeds. However, the regulatory mechanism of the effect of drying temperature on vigor of rice seeds with high initial moisture content (IMC) has not been examined. RESULTS: This study presents hot-air drying of rice seeds with high IMC (>30%) to assess the effect of drying temperature (35, 41, and 47 °C) on drying performance and seed vigor in terms of germination capacity. The results show a significant positive correlation between the drying rate, seed temperature, and drying temperature. High-temperature drying tends to cause a large accumulation of reactive oxygen species (ROS) and increases the activity of antioxidant enzymes in rice seeds. High-temperature drying also significantly increased abscisic acid (ABA) content and decreased gibberellin (GA) content through the regulation of the activity of metabolism related-enzymes. Moreover, changes in GA and ABA metabolism during early seed germination might be an important reason for the decrease in seed vigor with high-temperature drying. High-temperature drying also significantly inhibited the activity of α-amylase during early seed germination. CONCLUSION: A drying temperature of 35 °C was safe for rice seeds with high IMC, whereas higher drying temperatures (41 and 47 °C) reduced rice seed vigor remarkably. The metabolism of ROS, antioxidant enzymes, GA, ABA, and α-amylase might be closely involved in the regulation of the effect of drying temperature on the seed vigor of rice seeds with high IMC. The results of this study, therefore, provide a theoretical basis and technical guidance for mechanical drying of rice seeds. © 2020 Society of Chemical Industry.
Assuntos
Oryza/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Proteínas de Plantas/genética , Espécies Reativas de Oxigênio/metabolismo , Sementes/química , Ácido Abscísico/metabolismo , Regulação da Expressão Gênica de Plantas , Germinação , Giberelinas/metabolismo , Oryza/química , Oryza/genética , Oryza/crescimento & desenvolvimento , Proteínas de Plantas/metabolismo , Sementes/genética , Sementes/crescimento & desenvolvimento , Sementes/metabolismo , Temperatura , alfa-Amilases/genética , alfa-Amilases/metabolismoRESUMO
L-amino acids represent the most common amino acid form, most notably as protein residues, whereas D-amino acids, despite their rare occurrence, play significant roles in many biological processes. Amino acid racemases are enzymes that catalyze the interconversion of L- and/or D-amino acids. McyF is a pyridoxal 5'-phosphate (PLP) independent amino acid racemase that produces the substrate D-aspartate for the biosynthesis of microcystin in the cyanobacterium Microcystis aeruginosa PCC7806. Here we report the crystal structures of McyF in complex with citrate, L-Asp and D-Asp at 2.35, 2.63 and 2.80â¯Å, respectively. Structural analyses indicate that McyF and homologs possess highly conserved residues involved in substrate binding and catalysis. In addition, residues Cys87 and Cys195 were clearly assigned to the key catalytic residues of "two bases" that deprotonate D-Asp and L-Asp in a reaction independent of PLP. Further site-directed mutagenesis combined with enzymatic assays revealed that Glu197 also participates in the catalytic reaction. In addition, activity assays proved that McyF could also catalyze the interconversion of L-MeAsp between D-MeAsp, the precursor of another microcystin isoform. These findings provide structural insights into the catalytic mechanism of aspartate racemase and microcystin biosynthesis.
Assuntos
Isomerases de Aminoácido/metabolismo , Microcystis/enzimologia , Biocatálise , Cristalografia por Raios X , Modelos Moleculares , Especificidade por SubstratoRESUMO
Invertases catalyze the hydrolysis of sucrose to glucose and fructose, thereby playing a key role in primary metabolism and plant development. According to the optimum pH, invertases are classified into acid invertases (Ac-Invs) and alkaline/neutral invertases (A/N-Invs), which share no sequence homology. Compared with Ac-Invs that have been extensively studied, the structure and catalytic mechanism of A/N-Invs remain unknown. Here we report the crystal structures of Anabaena alkaline invertase InvA, which was proposed to be the ancestor of modern plant A/N-Invs. These structures are the first in the GH100 family. InvA exists as a hexamer in both crystal and solution. Each subunit consists of an (α/α)6 barrel core structure in addition to an insertion of three helices. A couple of structures in complex with the substrate or products enabled us to assign the subsites -1 and +1 specifically binding glucose and fructose, respectively. Structural comparison combined with enzymatic assays indicated that Asp-188 and Glu-414 are putative catalytic residues. Further analysis of the substrate binding pocket demonstrated that InvA possesses a stringent substrate specificity toward the α1,2-glycosidic bond of sucrose. Together, we suggest that InvA and homologs represent a novel family of glucosidases.
Assuntos
Anabaena/enzimologia , Proteínas de Bactérias/química , beta-Frutofuranosidase/química , Anabaena/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cristalografia por Raios X , Frutose/química , Frutose/metabolismo , Glucose/química , Glucose/metabolismo , Domínios Proteicos , Sacarose/química , Sacarose/metabolismo , beta-Frutofuranosidase/genética , beta-Frutofuranosidase/metabolismoRESUMO
BACKGROUND: Timely harvest is critical for hybrid rice to achieve maximum seed viability, vigor and yield. However, how to predict the optimum harvest time has been rarely reported so far. RESULTS: The seed vigor of Zhuliangyou 06 (ZLY06) increased and reached the highest level at 20 days after pollination (DAP), when seed moisture content had a lower value, which was maintained until final seed maturation. For Chunyou 84 (CY84), seed vigor, fresh and dry weight had relatively high values at 25 DAP, when seed moisture content reached the lowest value and changed slightly from 25 to 55 DAP. In both hybrid rice varieties, seed glume chlorophyll content declined rapidly from 10 to 30 DAP and remained at a very low level after 35 DAP. Starch content exhibited an increasing trend during seed maturation, while both soluble sugar content and amylase activity decreased significantly at the early stages of seed development. Moreover, correlation analyses showed that seed dry weight, starch content and superoxide dismutase activity were significantly positively correlated with seed vigor. In contrast, chlorophyll content, moisture content, soluble sugar, soluble protein, abscisic acid, gibberellin content, electrical conductivity, catalase and ascorbate peroxidase activities were significantly negatively correlated with seed vigor. Physiological and biochemical parameters were obviously more closely related with seed vigor than with seed germinability during seed development. CONCLUSION: Seed vigor could be better used as a comprehensive factor to predict the optimum seed harvest time. It is suggested that for ZLY06 seeds could be harvested as early as 20 DAP, whereas for CY84 the earliest optimum harvest time was 25 DAP. © 2016 Society of Chemical Industry.
Assuntos
Agricultura/métodos , Aptidão Genética , Germinação , Hibridização Genética , Oryza/crescimento & desenvolvimento , Melhoramento Vegetal , Sementes/crescimento & desenvolvimento , Ácido Abscísico/metabolismo , Biomassa , Metabolismo dos Carboidratos , Catalase/metabolismo , Clorofila/metabolismo , Giberelinas/metabolismo , Humanos , Vigor Híbrido , Oryza/genética , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Sementes/metabolismo , Amido/metabolismo , Superóxido Dismutase/metabolismoRESUMO
BACKGROUND: During the production of early hybrid rice seed, the seeds dehydrated slowly and retained high moisture levels when rainy weather lasted for a couple of days, and the rice seeds easily occurred pre-harvest sprouting (PHS) along with high temperature. Therefore it is necessary to harvest the seeds before the PHS occurred. RESULTS: The seeds of hybrid rice (Oryza sativa L. subsp. indica) cv. Qianyou No1 that harvests from 19 to 28 days after pollination (DAP) all had high seed vigour. The seed moisture content at 10 DAP was 36.1%, and declined to 28.6% at 19 DAP; the contents of soluble sugar and total starch increased significantly with the development of seeds. The soluble protein content, the level of abscisic acid (ABA) and gibberellin (GA3 ), and ascorbate peroxidase (APX) activity continued to decrease from 10 DAP to 19 DAP. The seeds at 19 DAP had the highest peroxidase (POD) activity and lowest catalase (CAT) activity while the superoxide dismutase (SOD) activity had no significant difference among the different developing periods. The relative expressions of genes 64S Hsp18.0 and Os03g0267200 transcripts increased significantly from 10 to 19 DAP, and then decreased. However, no significant change was recorded in soluble protein, sugar and GA3 after 16 DAP, and they all significantly correlated with seed viability and vigour during the process of seed maturity. CONCLUSION: The seeds of hybrid rice Qianyou No1 had a higher viability and vigour when harvested from 19 DAP to 28 DAP, the transcription levels of 64S Hsp18.0 and Os03g0267200 increased significantly from 10 DAP to 19 DAP and the highest value was recorded at 19 DAP. The seeds could be harvested as early as 19 DAP without negative influence on seed vigour and viability.
Assuntos
Regulação da Expressão Gênica de Plantas/fisiologia , Germinação/fisiologia , Proteínas de Choque Térmico/metabolismo , Oryza/genética , Oryza/fisiologia , Sementes/metabolismo , Ácido Abscísico/metabolismo , Giberelinas/metabolismo , Proteínas de Choque Térmico/genética , Hibridização Genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Sementes/genéticaRESUMO
The combination of a new bifunctional phosphine and an acrylate generate a zwitterion inâ situ and it serves as an efficient catalyst for asymmetric reactions through a homogeneous ion-pairing mode. This new catalytic system has been successfully applied to Mannich-type reactions to give excellent results and it demonstrates a broad substrate scope. Such reactivity is not accessible with general organophosphine catalytic modes. Preliminary investigations into the mechanism are also presented.
RESUMO
Saccharomyces cerevisiae Coq5 is an S-adenosyl methionine (SAM)-dependent methyltransferase (SAM-MTase) that catalyzes the only C-methylation step in the coenzyme Q (CoQ) biosynthesis pathway, in which 2-methoxy-6-polyprenyl-1,4-benzoquinone (DDMQH2) is converted to 2-methoxy-5-methyl-6-polyprenyl-1,4-benzoquinone (DMQH2). Crystal structures of Coq5 were determined in the apo form (Coq5-apo) at 2.2â Å resolution and in the SAM-bound form (Coq5-SAM) at 2.4â Å resolution, representing the first pair of structures for the yeast CoQ biosynthetic enzymes. Coq5 displays a typical class I SAM-MTase structure with two minor variations beyond the core domain, both of which are considered to participate in dimerization and/or substrate recognition. Slight conformational changes at the active-site pocket were observed upon binding of SAM. Structure-based computational simulation using an analogue of DDMQH2 enabled us to identify the binding pocket and entrance tunnel of the substrate. Multiple-sequence alignment showed that the residues contributing to the dimeric interface and the SAM- and DDMQH2-binding sites are highly conserved in Coq5 and homologues from diverse species. A putative catalytic mechanism of Coq5 was proposed in which Arg201 acts as a general base to initiate catalysis with the help of a water molecule.
Assuntos
Cristalografia por Raios X/métodos , Metiltransferases/química , Proteínas de Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/metabolismo , Ubiquinona/biossíntese , Catálise , Metiltransferases/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Especificidade por Substrato , Ubiquinona/metabolismoRESUMO
Human cortical neurons (hCNs) exhibit high dendritic complexity and synaptic density, and the maturation process is greatly protracted. However, the molecular mechanism governing these specific features remains unclear. Here, we report that the hominoid-specific gene TBC1D3 promotes dendritic arborization and protracts the pace of synaptogenesis. Ablation of TBC1D3 in induced hCNs causes reduction of dendritic growth and precocious synaptic maturation. Forced expression of TBC1D3 in the mouse cortex protracts synaptic maturation while increasing dendritic growth. Mechanistically, TBC1D3 functions via interaction with MICAL1, a monooxygenase that mediates oxidation of actin filament. At the early stage of differentiation, the TBC1D3/MICAL1 interaction in the cytosol promotes dendritic growth via F-actin oxidation and enhanced actin dynamics. At late stages, TBC1D3 escorts MICAL1 into the nucleus and downregulates the expression of genes related with synaptic maturation through interaction with the chromatin remodeling factor ATRX. Thus, this study delineates the molecular mechanisms underlying human neuron development.
RESUMO
Seed vigor is a key factor affecting seed quality. The mechanical drying process exerts a significant influence on rice seed vigor. The initial moisture content (IMC) and drying temperature are considered the main factors affecting rice seed vigor through mechanical drying. This study aimed to determine the optimum drying temperature for rice seeds according to the IMC, and elucidate the mechanisms mediating the effects of drying temperature and IMC on seed vigor. Rice seeds with three different IMCs (20%, 25%, and 30%) were dried to the target moisture content (14%) at four different drying temperatures. The results showed that the drying temperature and IMC had significant effects on the drying performance and vigor of the rice seeds. The upper limits of drying temperature for rice seeds with 20%, 25%, and 30% IMCs were 45, 42, and 38 °C, respectively. The drying rate and seed temperature increased significantly with increasing drying temperature. The drying temperature, drying rate, and seed temperature showed extremely significant negative correlations with germination energy (GE), germination rate, germination index (GI), and vigor index (VI). A high IMC and drying temperature probably induced a massive accumulation of hydrogen peroxide (H2O2) and superoxide anions in the seeds, enhanced superoxide dismutase (SOD) and catalase (CAT) activity, and increased the abscisic acid (ABA) content. In the early stage of seed germination, the IMC and drying temperature regulated seed germination through the metabolism of H2O2, gibberellin acid (GA), ABA, and α-amylase. These results indicate that the metabolism of reactive oxygen species (ROS), antioxidant enzymes, GA, ABA, and α-amylase might be involved in the mediation of the effects of drying temperature on seed vigor. The results of this study provide a theoretical basis and technical guidance for the mechanical drying of rice seeds.
Assuntos
Ácido Abscísico/metabolismo , Antioxidantes/metabolismo , Germinação , Giberelinas/metabolismo , Oryza/metabolismo , Sementes/metabolismo , Antioxidantes/química , Antioxidantes/farmacologia , Catalase/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Peróxido de Hidrogênio/química , Malondialdeído/química , Oxigênio/química , Proteínas de Plantas/genética , Espécies Reativas de Oxigênio , Superóxido Dismutase/metabolismo , Superóxidos/química , Temperatura , Tempo (Meteorologia) , alfa-Amilases/metabolismoRESUMO
The changes of kernel nutritive components and seed vigor in F1 seeds of sh2 sweet corn during seed development stage were investigated and the relationships between them were analyzed by time series regression (TSR) analysis. The results show that total soluble sugar and reducing sugar contents gradually declined, while starch and soluble protein contents increased throughout the seed development stages. Germination percentage, energy of germination, germination index and vigor index gradually increased along with seed development and reached the highest levels at 38 d after pollination (DAP). The TSR showed that, during 14 to 42 DAP, total soluble sugar content was independent of the vigor parameters determined in present experiment, while the reducing sugar content had a significant effect on seed vigor. TSR equations between seed reducing sugar and seed vigor were also developed. There were negative correlations between the seed reducing sugar content and the germination percentage, energy of germination, germination index and vigor index, respectively. It is suggested that the seed germination, energy of germination, germination index and vigor index could be predicted by the content of reducing sugar in sweet corn seeds during seed development stages.
Assuntos
Sementes/crescimento & desenvolvimento , Zea mays/crescimento & desenvolvimento , Carboidratos/análise , Germinação , Zea mays/químicaRESUMO
Following the Aeromonas hydrophila aerolysin, various aerolysin-like pore-forming proteins have been identified from bacteria to vertebrates. We have recently reported the mechanism of receptor recognition and in vitro pore-formation of a zebrafish aerolysin-like protein Dln1/Aep1. However, the physiological function of Aep1 remains unknown. Here we detected that aep1 gene is constitutively expressed in various immune-related tissues of adult zebrafish; and moreover, its expression is significantly up-regulated upon bacterial challenge, indicating its involvement in antimicrobial infection. Pre-injection of recombinant Aep1 into the infected zebrafish greatly accelerated the clearance of bacteria, resulting in significantly increased survival rate. Meanwhile, the induced expression of cytokines such as interleukin IL-1ß and tumor necrosis factor TNF-α in zebrafish upon injection of recombinant Aep1 suggested that Aep1 may be a pro-inflammatory protein that triggers the antimicrobial immune responses. However, compared to the overproduction of these cytokines in the infected zebrafish, pre-injection of Aep1 could significantly reduce the expression level of these cytokines, accompanying with a reduced bacterial load. Moreover, the expression profiles through the developmental stages of zebrafish demonstrated that aep1 is activated at the very early stage prior to the maturation of adaptive immune system. Altogether, our findings proved that Aep1 is an innate immune molecule that prevents the bacterial infection.
Assuntos
Toxinas Bacterianas/metabolismo , Proteínas Citotóxicas Formadoras de Poros/metabolismo , Infecções Estafilocócicas/imunologia , Staphylococcus aureus/imunologia , Proteínas de Peixe-Zebra/metabolismo , Peixe-Zebra/imunologia , Imunidade Adaptativa/genética , Aeromonas hydrophila/genética , Animais , Toxinas Bacterianas/genética , Células Cultivadas , Regulação da Expressão Gênica no Desenvolvimento , Imunidade Inata , Mediadores da Inflamação/metabolismo , Interleucina-1beta/metabolismo , Filogenia , Proteínas Citotóxicas Formadoras de Poros/genética , Fator de Necrose Tumoral alfa/metabolismo , Proteínas de Peixe-Zebra/genéticaRESUMO
Discovery of variable lymphocyte receptors (VLRs) in agnathans (jawless fish) has brought the origin of adaptive immunity system (AIS) forward to 500 million years ago accompanying with the emergence of vertebrates. Previous findings indicated that amphioxus, a representative model organism of chordate, also possesses some homologs of the basic components of TCR/BCR-based AIS, but it remains unknown if there exist any components of VLR-based AIS in amphioxus. Bioinformatics analyses revealed the amphioxus Branchiostoma floridae encodes a group of putative VLR-like proteins. Here we reported the 1.79 Å crystal structure of Bf66946, which forms a crescent-shaped structure of five leucine-rich repeats (LRRs). Structural comparisons indicated that Bf66946 resembles the lamprey VLRC. Further electrostatic potential analyses showed a negatively-charged patch at the concave of LRR solenoid structure that might be responsible for antigen recognition. Site-directed mutagenesis combined with bacterial binding assays revealed that Bf66946 binds to the surface of Gram-positive bacteria Staphylococcus aureus and Streptococcus pneumonia via a couple of acidic residues at the concave. In addition, the closest homolog of Bf66946 is highly expressed in the potential immune organ gill of Branchiostoma belcheri. Altogether, our findings provide the first structural evidence for the emergence of VLR-like molecules in the basal chordates.
Assuntos
Anfioxos , Modelos Moleculares , Conformação Proteica , Receptores de Antígenos/química , Sequência de Aminoácidos , Animais , Biologia Computacional , Sequência Conservada , Brânquias/metabolismo , Anfioxos/metabolismo , Peptidoglicano/química , Peptidoglicano/metabolismo , Ligação Proteica , Receptores de Antígenos/metabolismoRESUMO
Glutaredoxins (Grxs) constitute a superfamily of proteins that perform diverse biological functions. The Saccharomyces cerevisiae glutaredoxin Grx6 not only serves as a glutathione (GSH)-dependent oxidoreductase and as a GSH transferase, but also as an essential [2Fe-2S]-binding protein. Here, the dimeric structure of the C-terminal domain of Grx6 (holo Grx6C), bridged by one [2Fe-2S] cluster coordinated by the active-site Cys136 and two external GSH molecules, is reported. Structural comparison combined with multiple-sequence alignment demonstrated that holo Grx6C is similar to the [2Fe-2S] cluster-incorporated dithiol Grxs, which share a highly conserved [2Fe-2S] cluster-binding pattern and dimeric conformation that is distinct from the previously identified [2Fe-2S] cluster-ligated monothiol Grxs.
Assuntos
Complexos de Coordenação/química , Glutarredoxinas/química , Glutationa/química , Ferro/química , Proteínas de Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/química , Enxofre/química , Sequência de Aminoácidos , Domínio Catalítico , Clonagem Molecular , Complexos de Coordenação/metabolismo , Cristalografia por Raios X , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Glutarredoxinas/genética , Glutarredoxinas/metabolismo , Glutationa/metabolismo , Ferro/metabolismo , Modelos Moleculares , Plasmídeos/química , Plasmídeos/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/enzimologia , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Enxofre/metabolismoRESUMO
The mechanisms by which the eggs of the Antarctic notothenioid fishes avoid freezing are not fully understood. Zona pellucida proteins (ZPs) are constituents of the chorion which forms a protective matrix surrounding the egg. Here we report occurrence of freezing temperature-related gene expansion and acquisition of unusual ice melting-promoting (IMP) activity in a family of Antarctic notothenioid ZPs (AnnotoZPs). Members of AnnotoZPs are shown to bind with ice and non-colligatively depress the melting point of a solution in a range of 0.26 to 0.65 °C at a moderate concentration. Eggs of zebrafishes expressing an AnnotoZP transgene show improved melting point depression and enhanced survival in freezing conditions. Mutational analyses in a representative AnnotoZP indicate the ZP domain and patches of acidic residues are essential structures for the IMP activity. AnnotoZPs, therefore, represent a group of macromolecules that prevent freezing by a unique ZP-ice interaction mechanism distinct from the known antifreeze proteins.
Assuntos
Adaptação Fisiológica , Proteínas Anticongelantes/fisiologia , Congelamento , Oócitos/fisiologia , Peixe-Zebra/fisiologia , Zona Pelúcida/fisiologia , Animais , Regiões Antárticas , Temperatura Baixa , Análise Mutacional de DNA , Etiquetas de Sequências Expressas , Genoma , Modelos Moleculares , Filogenia , Conformação Proteica , Proteínas Recombinantes/metabolismo , Temperatura , Transgenes , Peixe-Zebra/genéticaRESUMO
Peptidoglycan recognition proteins (PGRPs), which have been identified in most animals, are pattern recognition molecules that involve antimicrobial defense. Resulting from extraordinary expansion of innate immune genes, the amphioxus encodes many PGRPs of diverse functions. For instance, three isoforms of PGRP encoded by Branchiostoma belcheri tsingtauense, termed BbtPGRP1~3, are fused with a chitin binding domain (CBD) at the N-terminus. Here we report the 2.7 Å crystal structure of BbtPGRP3, revealing an overall structure of an N-terminal hevein-like CBD followed by a catalytic PGRP domain. Activity assays combined with site-directed mutagenesis indicated that the individual PGRP domain exhibits amidase activity towards both DAP-type and Lys-type peptidoglycans (PGNs), the former of which is favored. The N-terminal CBD not only has the chitin-binding activity, but also enables BbtPGRP3 to gain a five-fold increase of amidase activity towards the Lys-type PGNs, leading to a significantly broadened substrate spectrum. Together, we propose that modular evolution via domain shuffling combined with gene horizontal transfer makes BbtPGRP1~3 novel PGRPs of augmented catalytic activity and broad recognition spectrum.
Assuntos
Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Quitina/metabolismo , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Sequência de Aminoácidos , Animais , Proteínas de Transporte/genética , Evolução Molecular , Anfioxos , Modelos Moleculares , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão/genéticaRESUMO
Tea (Camellia sinensis L.) seed shells, the main byproduct of the manufacture of tea seed oil, were used as precursors for the preparation of tea activated carbon (TAC) in the present study. A high yield (44.1%) of TAC was obtained from tea seed shells via a one-step chemical method using ZnCl2 as an agent. The Brunauer-Emmett-Teller (BET) surface area and the total pore volumes of the obtained TAC were found to be 1530.67 mg(2)/g and 0.7826 cm(3)/g, respectively. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 324.7 mg/g for methylene blue. Adsorption kinetics studies indicated that the pseudo-second-order model yielded the best fit for the kinetic data. An intraparticle diffusion model suggested that the intraparticle diffusion was not the only rate-controlling step. Thermodynamics studies revealed the spontaneous and exothermic nature of the sorption process. These results indicate that tea seed shells could be utilized as a renewable resource to develop activated carbon which is a potential adsorbent for methylene blue.
Assuntos
Camellia sinensis/metabolismo , Carbono/química , Inibidores Enzimáticos/química , Azul de Metileno/química , Adsorção , Cátions , Cloretos/química , Difusão , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Poluentes Químicos da Água/química , Purificação da Água/métodos , Compostos de Zinco/químicaRESUMO
OBJECTIVE: To examine the mortality and risk factors among HIV-infected patients during 1989 - 2011 in Dehong prefecture, Yunnan province. METHODS: All HIV-infected patients reported during 1989 - 2011 in Dehong prefecture who held local residency were included in the study. Mortality rates and cumulative survival rates were calculated. Multiple regression analysis under Cox proportional hazard model was conducted to examine the risk factors for deaths. RESULTS: A total of 13 006 HIV-infected patients were included in this study including 73.2% males, 79.1% peasants and 48.7% married at the time of reporting. 64.5% of the patients were ethnic minorities, and 68.7% were illiterate or having received only primary school education. All the patients were followed-up for a total of 55 962.30 person-years with 4648 patients died, with overall mortality rate as 8.31/100 person-years. The mortality rate had been increasing from 1990 to 2004 but decreasing since 2005. The average survival time since the identification of HIV infection was 9.48 years overall, and was 16.65 years for those having received antiretroviral treatment (ART) and 7.67 years for those without ART. Data from multiple regression analysis indicated that ART and socio-demographic characteristics such as age, gender, ethnicity, occupation, marital status, education background etc. were significantly associated with death among HIV-infected patients. CONCLUSION: The comprehensive AIDS campaigns including ART had significantly reduced the deaths among HIV-infected patients in Dehong prefecture. More efforts on the scaling up program of ART as well as the enhanced management and follow-up program tailored for HIV-infected patients with different socio-demographic characteristics were needed to further reduce the deaths in the area.