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On page 1 showing 1 ~ 20 papers out of 31 papers

X chromosome protects against bladder cancer in females via a KDM6A-dependent epigenetic mechanism.

  • Satoshi Kaneko‎ et al.
  • Science advances‎
  • 2018‎

Men are much more likely than women to develop bladder cancer (BCa), but the underlying cause of this gender disparity remains poorly defined. Using sex-reversed mice, we show that the sex chromosome complement is an independent cause and, moreover, amplifies the biasing effects of sex hormones. We also show that the X-linked lysine demethylase 6A (KDM6A) is a sexually dimorphic gene. Wild-type but not catalytically dead KDM6A confers sustained tumor suppressor activity in vitro. Knockout of mouse Kdm6a reduces expression of Cdkn1a and Perp, canonical gene targets of the tumor suppressor p53. Consistently, loss of Kdm6a increases BCa risk in female mice, and mutations or reduced expression of human KDM6A predicts poor prognosis of female BCa patients. Collectively, the study reveals that the X chromosome protects against BCa among females via a KDM6A-dependent epigenetic mechanism and further suggests that KDM6A is a prototypical sex-biasing tumor suppressor with both demethylase-dependent and demethylase-independent activities.


Heterologous expression and characterization of an Arabidopsis β-l-arabinopyranosidase and α-d-galactosidases acting on β-l-arabinopyranosyl residues.

  • Chiemi Imaizumi‎ et al.
  • Journal of experimental botany‎
  • 2017‎

The major plant sugar l-arabinose (l-Ara) has two different ring forms, l-arabinofuranose (l-Araf) and l-arabinopyranose (l-Arap). Although l-Ara mainly appears in the form of α-l-Araf residues in cell wall components, such as pectic α-1,3:1,5-arabinan, arabinoxylan, and arabinogalactan-proteins (AGPs), lesser amounts of it can also be found as β-l-Arap residues of AGPs. Even though AGPs are known to be rapidly metabolized, the enzymes acting on the β-l-Arap residues remain to be identified. In the present study, four enzymes, which we call β-l-ARAPASE (APSE) and α-GALACTOSIDASE 1 (AGAL1), AGAL2, and AGAL3, are identified as those enzymes that are likely to be responsible for the hydrolysis of the β-l-Arap residues in Arabidopsis thaliana. An Arabidopsis apse-1 mutant showed significant reduction in β-l-arabinopyranosidase activity, and an apse-1 agal3-1 double-mutant exhibited even less activity. The apse-1 and the double-mutants both had more β-l-Arap residues in the cell walls than wild-type plants. Recombinant APSE expressed in the yeast Pichia pastoris specifically hydrolyzed β-l-Arap residues and released l-Ara from gum arabic and larch arabinogalactan. The recombinant AGAL3 also showed weak β-l-arabinopyranosidase activity beside its strong α-galactosidase activity. It appears that the β-l-Arap residues of AGPs are hydrolysed mainly by APSE and partially by AGALs in Arabidopsis.


Zonisamide attenuates the severity of levodopa-induced dyskinesia via modulation of the striatal serotonergic system in a rat model of Parkinson's disease.

  • Rie Tohge‎ et al.
  • Neuropharmacology‎
  • 2021‎

Glutamate, GABA, acetylcholine, dopamine, and serotonin interact with each other to regulate the flow of neural information in the striatum. Serotonin type 1A receptor (5HT1A) is primarily expressed on glutamatergic nerve terminals, and 5HT1B is expressed on GABAergic medium spiny neurons (MSNs). Zonisamide (ZNS) reportedly improves the off period without worsening levodopa-induced dyskinesia (LID) in patients with advanced Parkinson's disease. In this study, LID model rats were prepared by administrating levodopa to unilaterally 6-OHDA-lesioned rats. We analyzed changes in serotonergic neurotransmission of LID model rats to elucidate the relationship between LID and the serotonergic system and pathomechanism of the anti-dyskinetic effects of ZNS. Abnormal involuntary movements (AIMs) were most severe in intermittently levodopa-treated rats but milder in rats intermittently medicated with levodopa and ZNS. Continuously levodopa-infused rats or intermittently ZNS-injected rats did not develop AIMs, and no differences in the expression of brain-derived neurotrophic factor, 5-HT transporter, 5HT1A, and 5HT1B mRNA between the lesioned striatum and normal side were observed. Expression of 5HT1B mRNA was elevated in the lesioned striatum of intermittently levodopa-treated rats, but this elevation was normalized by concomitant use of ZNS. The severity of AIMs was correlated with the ratio of 5HT1B to 5HT1A mRNA expression in the lesioned striatum, indicating that the anti-LID effect of ZNS is based on inhibition via 5HT1B receptors to direct pathway MSNs sensitized by intermittent levodopa treatment. Selectively acting serotonergic drugs, especially those that lower the 5HT1B to 5HT1A ratio, are promising new therapeutic agents to attenuate LID development.


Impact of integrated water, sanitation, hygiene, health and nutritional interventions on diarrhoea disease epidemiology and microbial quality of water in a resource-constrained setting in Kenya: A controlled intervention study.

  • Ernest Apondi Wandera‎ et al.
  • Tropical medicine & international health : TM & IH‎
  • 2022‎

We assessed the impact of water, hygiene and sanitation (WASH), maternal, new-born and child health (MNCH), nutrition and early childhood development (ECD) on diarrhoea and microbial quality of water in a resource-constrained rural setting in Kenya.


Evaluation of Two Sets of Sorghum Bagasse Samples as the Feedstock for Fermentable Sugar Recovery via the Calcium Capturing by Carbonation (CaCCO) Process.

  • Riki Shiroma‎ et al.
  • Journal of applied glycoscience‎
  • 2016‎

Sorghum bagasse samples from two sets (n6 and bmr6; n18 and bmr18) of wild-type and corresponding "brown midrib" (bmr) mutant strains of sweet sorghum were evaluated as the feedstock for fermentable sugar recovery via the calcium capturing by carbonation (CaCCO) process, which involves Ca(OH)2 pretreatment of bagasse with subsequent neutralization with CO2 for enzymatic saccharification. Saccharification tests under various pretreatment conditions of the CaCCO process at different Ca(OH)2 concentrations, temperatures or residence periods indicated that bmr strains are more sensitive to the pretreatment than their counterparts are. It is expected that variant bmr6 is more suitable for glucose recovery than its wild-type counterpart because of the higher glucan content and better glucose recovery with less severe pretreatment. Meanwhile, bmr18showed higher scores of glucose recovery than its counterpart did, only at low pretreatment severity, and did not yield higher sugar recovery under the more severe conditions. The trend was similar to that of xylose recovery data from the two bmr strains. The advantages of bmr strains were also proven by means of simultaneous saccharification and fermentation of CaCCO-pretreated bagasse samples by pentose-fermenting yeast strain Candida shehatae Cs 4R. The amounts needed for production of 1 L of ethanol from n6, bmr6, n18, and bmr18samples were estimated as 4.11, 3.46, 4.03, and 3.95 kg, respectively. The bmr strains seem to have excellent compatibility with the CaCCO process for ethanol production, and it is expected that integrated research from the feedstock to bioprocess may result in breakthroughs for commercialization.


A novel family of hemicellulolytic alpha-glucuronidase.

  • Olena Ryabova‎ et al.
  • FEBS letters‎
  • 2009‎

Investigation of the xylanolytic enzyme system of the xylose-fermenting yeast Pichia stipitis resulted in the discovery of an extracellular alpha-glucuronidase efficiently debranching hardwood glucuronoxylan. This activity is not exhibited by more extensively investigated alpha-glucuronidases of glycoside hydrolase (GH) family 67, operating on substrates in which the uronic acid is linked to the non-reducing xylopyranosyl residues of main chain fragments. The N-terminus of the purified enzyme corresponded exactly to the P. stipitis gene ABN67901 coding for a protein of unknown function. BLAST search revealed the presence of similar genes in genomes of other microorganisms. These results lead to the emergence of a new family of alpha-glucuronidases.


TGF- β Signaling Cooperates with AT Motif-Binding Factor-1 for Repression of the α -Fetoprotein Promoter.

  • Nobuo Sakata‎ et al.
  • Journal of signal transduction‎
  • 2014‎

α-Fetoprotein (AFP) is known to be highly produced in fetal liver despite its barely detectable level in normal adult liver. On the other hand, hepatocellular carcinoma often shows high expression of AFP. Thus, AFP seems to be an oncogenic marker. In our present study, we investigated how TGF-β signaling cooperates with AT motif-binding factor-1 (ATBF1) to inhibit AFP transcription. Indeed, the expression of AFP mRNA in HuH-7 cells was negatively regulated by TGF-β signaling. To further understand how TGF-β suppresses the transcription of the AFP gene, we analyzed the activity of the AFP promoter in the presence of TGF-β. We found that the TGF-β signaling and ATBF1 suppressed AFP transcription through two ATBF1 binding elements (AT-motifs). Using a heterologous reporter system, both AT-motifs were required for transcriptional repression upon TGF-β stimulation. Furthermore, Smads were found to interact with ATBF1 at both its N-terminal and C-terminal regions. Since the N-terminal (ATBF1N) and C-terminal regions of ATBF1 (ATBF1C) lack the ability of DNA binding, both truncated mutants rescued the cooperative inhibitory action by the TGF-β signaling and ATBF1 in a dose-dependent manner. Taken together, these findings indicate that TGF-β signaling can act in concert with ATBF1 to suppress the activity of the AFP promoter through direct interaction of ATBF1 with Smads.


Dynamics of serological responses to defined recombinant proteins during Schistosoma mansoni infection in mice before and after the treatment with praziquantel.

  • Eman Sayed Mohammed‎ et al.
  • PLoS neglected tropical diseases‎
  • 2020‎

To eliminate schistosomiasis, appropriate diagnostic tests are required to monitor its prevalence and transmission, especially in the settings with low endemicity resulting from the consecutive mass drug administration. Antibodies that react with either crude soluble schistosome egg antigens or soluble worm antigen preparations have been used to monitor infection in low-prevalence regions. However, these detection methods cannot discriminate current and past infections and are cross-reactive with other parasites because both antigens contain numerous proteins and glycans from schistosomes, and standard preparations need maintenance of the life cycle of the schistosome. To evaluate the potential utility of nine recombinant Schistosoma mansoni proteins as single defined antigens for serological diagnosis, we monitored the kinetics of antibodies to each antigen during S. mansoni infection in mice before and after the treatment with praziquantel. C57BL/6 mice were infected with 50 cercariae. The levels of immunoglobulin G (IgG) raised against five recombinant antigens (RP26, sm31, sm32, GST, and LAP1) significantly increased as early as 2-4 weeks after infection and rapidly declined by 2 weeks after the treatment, whereas those raised against crude S. mansoni egg antigens or other antigens remained elevated long after the treatment. The IgG1 raised against RP26, sm31, and serpin decreased after the treatment with praziquantel, whereas the IgE raised against serpin declined strikingly after the treatment. This study clarifies the dynamics of the serological responses to recombinant S. mansoni proteins during infection and after the treatment with praziquantel and identifies several candidate antigens with potential utility in the monitoring and surveillance of schistosomiasis toward the elimination of schistosomiasis.


Detection of multiple mycetoma pathogens using fungal metabarcoding analysis of soil DNA in an endemic area of Sudan.

  • Hiroki Hashizume‎ et al.
  • PLoS neglected tropical diseases‎
  • 2022‎

Mycetoma is a tropical disease caused by several fungi and bacteria present in the soil. Fungal mycetoma and eumycetoma are especially challenging to treat; therefore, prevention, early diagnosis, and early treatment are important, but it is also necessary to understand the geographic distribution of these pathogenic fungi. In this study, we used DNA metabarcoding methodology to identify fungal species from soil samples. Soil sampling was implemented at seven villages in an endemic area of Sennar State in Sudan in 2019, and ten sampling sites were selected in each village according to land-use conditions. In total, 70 soil samples were collected from ground surfaces, and DNA in the soil was extracted with a combined method of alkaline DNA extraction and a commercial soil DNA extraction kit. The region for universal primers was selected to be the ribosomal internal transcribed spacer one region for metabarcoding. After the second PCR for DNA library preparation, the amplicon-based DNA analysis was performed using next-generation sequencing with two sets of universal primers. A total of twelve mycetoma-causative fungal species were identified, including the prime agent, Madurella mycetomatis, and additional pathogens, Falciformispora senegalensis and Falciformispora tompkinsii, in 53 soil samples. This study demonstrated that soil DNA metabarcoding can elucidate the presence of multiple mycetoma-causative fungi, which may contribute to accurate diagnosis for patient treatment and geographical mapping.


Unique active-site and subsite features in the arabinogalactan-degrading GH43 exo-β-1,3-galactanase from Phanerochaete chrysosporium.

  • Kaori Matsuyama‎ et al.
  • The Journal of biological chemistry‎
  • 2020‎

Arabinogalactan proteins (AGPs) are plant proteoglycans with functions in growth and development. However, these functions are largely unexplored, mainly because of the complexity of the sugar moieties. These carbohydrate sequences are generally analyzed with the aid of glycoside hydrolases. The exo-β-1,3-galactanase is a glycoside hydrolase from the basidiomycete Phanerochaete chrysosporium (Pc1,3Gal43A), which specifically cleaves AGPs. However, its structure is not known in relation to its mechanism bypassing side chains. In this study, we solved the apo and liganded structures of Pc1,3Gal43A, which reveal a glycoside hydrolase family 43 subfamily 24 (GH43_sub24) catalytic domain together with a carbohydrate-binding module family 35 (CBM35) binding domain. GH43_sub24 is known to lack the catalytic base Asp conserved among other GH43 subfamilies. Our structure in combination with kinetic analyses reveals that the tautomerized imidic acid group of Gln263 serves as the catalytic base residue instead. Pc1,3Gal43A has three subsites that continue from the bottom of the catalytic pocket to the solvent. Subsite -1 contains a space that can accommodate the C-6 methylol of Gal, enabling the enzyme to bypass the β-1,6-linked galactan side chains of AGPs. Furthermore, the galactan-binding domain in CBM35 has a different ligand interaction mechanism from other sugar-binding CBM35s, including those that bind galactomannan. Specifically, we noted a Gly → Trp substitution, which affects pyranose stacking, and an Asp → Asn substitution in the binding pocket, which recognizes β-linked rather than α-linked Gal residues. These findings should facilitate further structural analysis of AGPs and may also be helpful in engineering designer enzymes for efficient biomass utilization.


High-density lipoprotein suppresses tumor necrosis factor alpha production by mycobacteria-infected human macrophages.

  • Manabu Inoue‎ et al.
  • Scientific reports‎
  • 2018‎

Immune responses to parasitic pathogens are affected by the host physiological condition. High-density lipoprotein (HDL) and low-density lipoprotein (LDL) are transporters of lipids between the liver and peripheral tissues, and modulate pro-inflammatory immune responses. Pathogenic mycobacteria are parasitic intracellular bacteria that can survive within macrophages for a long period. Macrophage function is thus key for host defense against mycobacteria. These basic facts suggest possible effects of HDL and LDL on mycobacterial diseases, which have not been elucidated so far. In this study, we found that HDL and not LDL enhanced mycobacterial infections in human macrophages. Nevertheless, we observed that HDL remarkably suppressed production of tumor necrosis factor alpha (TNF-α) upon mycobacterial infections. TNF-α is a critical host-protective cytokine against mycobacterial diseases. We proved that toll-like receptor (TLR)-2 is responsible for TNF-α production by human macrophages infected with mycobacteria. Subsequent analysis showed that HDL downregulates TLR2 expression and suppresses its intracellular signaling pathways. This report demonstrates for the first time the substantial action of HDL in mycobacterial infections to human macrophages.


Olopatadine suppresses the migration of THP-1 monocytes induced by S100A12 protein.

  • Kazuya Kishimoto‎ et al.
  • Mediators of inflammation‎
  • 2006‎

Olopatadine hydrochloride (olopatadine) is an antiallergic drug with histamine H(1) receptor antagonistic activity. Recently, olopatadine has been shown to bind to S100A12 which is a member of the S100 family of calcium-binding proteins, and exerts multiple proinflammatory activities including chemotaxis for monocytes and neutrophils. In this study, we examined the possibility that the interaction of olopatadine with S100A12 inhibits the proinflammatory effects of S100A12. Pretreatment of olopatadine with S100A12 reduced migration of THP-1, a monocyte cell line, induced by S100A12 alone, but did not affect recombinant human regulated upon activation, normal T cell expressed and secreted (RANTES)-induced migration. Amlexanox, which also binds to S100A12, inhibited the THP-1 migration induced by S100A12. However, ketotifen, another histamine H(1) receptor antagonist, had little effect on the activity of S100A12. These results suggest that olopatadine has a new mechanism of action, that is, suppression of the function of S100A12, in addition to histamine H(1) receptor antagonistic activity.


Novel pathogenic XK mutations in McLeod syndrome and interaction between XK protein and chorein.

  • Yuka Urata‎ et al.
  • Neurology. Genetics‎
  • 2019‎

To identify XK pathologic mutations in 6 patients with suspected McLeod syndrome (MLS) and a possible interaction between the chorea-acanthocytosis (ChAc)- and MLS-responsible proteins: chorein and XK protein.


Convergent evolution of processivity in bacterial and fungal cellulases.

  • Taku Uchiyama‎ et al.
  • Proceedings of the National Academy of Sciences of the United States of America‎
  • 2020‎

Cellulose is the most abundant biomass on Earth, and many microorganisms depend on it as a source of energy. It consists mainly of crystalline and amorphous regions, and natural degradation of the crystalline part is highly dependent on the degree of processivity of the degrading enzymes (i.e., the extent of continuous hydrolysis without detachment from the substrate cellulose). Here, we report high-speed atomic force microscopic (HS-AFM) observations of the movement of four types of cellulases derived from the cellulolytic bacteria Cellulomonas fimi on various insoluble cellulose substrates. The HS-AFM images clearly demonstrated that two of them (CfCel6B and CfCel48A) slide on crystalline cellulose. The direction of processive movement of CfCel6B is from the nonreducing to the reducing end of the substrate, which is opposite that of processive cellulase Cel7A of the fungus Trichoderma reesei (TrCel7A), whose movement was first observed by this technique, while CfCel48A moves in the same direction as TrCel7A. When CfCel6B and TrCel7A were mixed on the same substrate, "traffic accidents" were observed, in which the two cellulases blocked each other's progress. The processivity of CfCel6B was similar to those of fungal family 7 cellulases but considerably higher than those of fungal family 6 cellulases. The results indicate that bacteria utilize family 6 cellulases as high-processivity enzymes for efficient degradation of crystalline cellulose, whereas family 7 enzymes have the same function in fungi. This is consistent with the idea of convergent evolution of processive cellulases in fungi and bacteria to achieve similar functionality using different protein foldings.


4-O-Methyl Modifications of Glucuronic Acids in Xylans Are Indispensable for Substrate Discrimination by GH67 α-Glucuronidase from Bacillus halodurans C-125.

  • Haruka Yagi‎ et al.
  • Journal of applied glycoscience‎
  • 2017‎

A GH67 α-glucuronidase gene derived from Bacillus halodurans C-125 was expressed in E. coli to obtain a recombinant enzyme (BhGlcA67). Using the purified enzyme, the enzymatic properties and substrate specificities of the enzyme were investigated. BhGlcA67 showed maximum activity at pH 5.4 and 45 °C. When BhGlcA67 was incubated with birchwood, oat spelts, and cotton seed xylan, the enzyme did not release any glucuronic acid or 4-O-methyl-glucuronic acid from these substrates. BhGlcA67 acted only on 4-O-methyl-α-D-glucuronopyranosyl-(1→2)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranose (MeGlcA3Xyl3), which has a glucuronic acid side chain with a 4-O-methyl group located at its non-reducing end, but did not on β-D-xylopyranosyl-(1→4)-[4-O-methyl-α-D-glucuronopyranosyl-(l→2)]-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-xylop- yranose (MeGlcA3Xyl4) and α-D-glucuronopyranosyl-(l→2)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranose (GlcA3Xyl3). The environment for recognizing the 4-O-methyl group of glucuronic acid was observed in all the crystal structures of reported GH67 glucuronidases, and the amino acids for discriminating the 4-O-methyl group of glucuronic acid were widely conserved in the primary sequences of the GH67 family, suggesting that the 4-O-methyl group is critical for the activities of the GH67 family.


Functional Characterization of the GH10 and GH11 Xylanases from Streptomyces olivaceoviridis E-86 Provide Insights into the Advantage of GH11 Xylanase in Catalyzing Biomass Degradation.

  • Haruka Yagi‎ et al.
  • Journal of applied glycoscience‎
  • 2019‎

We functionally characterized the GH10 xylanase (SoXyn10A) and the GH11 xylanase (SoXyn11B) derived from the actinomycete Streptomyces olivaceoviridis E-86. Each enzyme exhibited differences in the produced reducing power upon degradation of xylan substrates. SoXyn10A produced higher reducing power than SoXyn11B. Gel filtration of the hydrolysates generated by both enzymes revealed that the original substrate was completely decomposed. Enzyme mixtures of SoXyn10A and SoXyn11B produced the same level of reducing power as SoXyn10A alone. These observations were in good agreement with the composition of the hydrolysis products. The hydrolysis products derived from the incubation of soluble birchwood xylan with a mixture of SoXyn10A and SoXyn11B produced the same products as SoXyn10A alone with similar compositions. Furthermore, the addition of SoXyn10A following SoXyn11B-mediated digestion of xylan produced the same products as SoXyn10A alone with similar compositions. Thus, it was hypothesized that SoXyn10A could degrade xylans to a smaller size than SoXyn11B. In contrast to the soluble xylans as the substrate, the produced reducing power generated by both enzymes was not significantly different when pretreated milled bagasses were used as substrates. Quantification of the pentose content in the milled bagasse residues after the enzyme digestions revealed that SoXyn11B hydrolyzed xylans in pretreated milled bagasses much more efficiently than SoXyn10A. These data suggested that the GH10 xylanases can degrade soluble xylans smaller than the GH11 xylanases. However, the GH11 xylanases may be more efficient at catalyzing xylan degradation in natural environments (e.g. biomass) where xylans interact with celluloses and lignins.


Species-Specific Serological Detection for Schistosomiasis by Serine Protease Inhibitor (SERPIN) in Multiplex Assay.

  • Chihiro Tanigawa‎ et al.
  • PLoS neglected tropical diseases‎
  • 2015‎

Both Schistosoma mansoni and Schistosoma haematobium cause schistosomiasis in sub-Saharan Africa. We assessed the diagnostic value of selected Schistosoma antigens for the development of a multiplex serological immunoassay for sero-epidemiological surveillance.


Regulation of proapoptotic mammalian ste20-like kinase MST2 by the IGF1-Akt pathway.

  • Donghwa Kim‎ et al.
  • PloS one‎
  • 2010‎

Hippo, a Drosophila serine/threonine kinase, promotes apoptosis and restricts cell growth and proliferation. Its mammalian homolog MST2 has been shown to play similar role and be regulated by Raf-1 via a kinase-independent mechanism and by RASSF family proteins through forming complex with MST2. However, regulation of MST2 by cell survival signal remains largely unknown.


Characterization of a modular enzyme of exo-1,5-alpha-L-arabinofuranosidase and arabinan binding module from Streptomyces avermitilis NBRC14893.

  • Hitomi Ichinose‎ et al.
  • Applied microbiology and biotechnology‎
  • 2008‎

A gene encoding an alpha-L-arabinofuranosidase, designated SaAraf43A, was cloned from Streptomyces avermitilis. The deduced amino acid sequence implies a modular structure consisting of an N-terminal glycoside hydrolase family 43 module and a C-terminal family 42 carbohydrate-binding module (CBM42). The recombinant enzyme showed optimal activity at pH 6.0 and 45 degrees C and was stable over the pH range of 5.0-6.5 at 30 degrees C. The enzyme hydrolyzed p-nitrophenol (PNP)-alpha-L-arabinofuranoside but did not hydrolyze PNP-alpha-L-arabinopyranoside, PNP-beta-D-xylopyranoside, or PNP-beta-D-galactopyranoside. Debranched 1,5-arabinan was hydrolyzed by the enzyme but arabinoxylan, arabinogalactan, gum arabic, and arabinan were not. Among the synthetic regioisomers of arabinofuranobiosides, only methyl 5-O-alpha-L-arabinofuranosyl-alpha-L-arabinofuranoside was hydrolyzed by the enzyme, while methyl 2-O-alpha-L-arabinofuranosyl-alpha-L-arabinofuranoside and methyl 3-O-alpha-L-arabinofuranosyl-alpha-L-arabinofuranoside were not. These data suggested that the enzyme only cleaves alpha-1,5-linked arabinofuranosyl linkages. The analysis of the hydrolysis product of arabinofuranopentaose suggested that the enzyme releases arabinose in exo-acting manner. These results indicate that the enzyme is definitely an exo-1,5-alpha-L-arabinofuranosidase. The C-terminal CBM42 did not show any affinity for arabinogalactan and debranched arabinan, although it bound arabinan and arabinoxylan, suggesting that the CBM42 bound to branched arabinofuranosyl residues. Removal of the module decreased the activity of the enzyme with regard to debranched arabinan. The CBM42 plays a role in enhancing the debranched arabinan hydrolytic action of the catalytic module in spite of its preference for binding arabinofuranosyl side chains.


Domain architecture divergence leads to functional divergence in binding and catalytic domains of bacterial and fungal cellobiohydrolases.

  • Akihiko Nakamura‎ et al.
  • The Journal of biological chemistry‎
  • 2020‎

Cellobiohydrolases directly convert crystalline cellulose into cellobiose and are of biotechnological interest to achieve efficient biomass utilization. As a result, much research in the field has focused on identifying cellobiohydrolases that are very fast. Cellobiohydrolase A from the bacterium Cellulomonas fimi (CfCel6B) and cellobiohydrolase II from the fungus Trichoderma reesei (TrCel6A) have similar catalytic domains (CDs) and show similar hydrolytic activity. However, TrCel6A and CfCel6B have different cellulose-binding domains (CBDs) and linkers: TrCel6A has a glycosylated peptide linker, whereas CfCel6B's linker consists of three fibronectin type 3 domains. We previously found that TrCel6A's linker plays an important role in increasing the binding rate constant to crystalline cellulose. However, it was not clear whether CfCel6B's linker has similar function. Here we analyze kinetic parameters of CfCel6B using single-molecule fluorescence imaging to compare CfCel6B and TrCel6A. We find that CBD is important for initial binding of CfCel6B, but the contribution of the linker to the binding rate constant or to the dissociation rate constant is minor. The crystal structure of the CfCel6B CD showed longer loops at the entrance and exit of the substrate-binding tunnel compared with TrCel6A CD, which results in higher processivity. Furthermore, CfCel6B CD showed not only fast surface diffusion but also slow processive movement, which is not observed in TrCel6A CD. Combined with the results of a phylogenetic tree analysis, we propose that bacterial cellobiohydrolases are designed to degrade crystalline cellulose using high-affinity CBD and high-processivity CD.


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