The Cytoskeletal Protein ��-Actinin Regulates Acid-sensing Ion Channel 1a through a C-terminal Interaction

The acid-sensing ion channel 1a (ASIC1a) is widely expressed in central and peripheral neurons where it generates transient cation currents when extracellular pH falls. ASIC1a confers pH-dependent modulation on postsynaptic dendritic spines and has critical effects in neurological diseases associated with a reduced pH. However, knowledge of the proteins that interact with ASIC1a and influence its function is limited. Here, we show that α-actinin, which links membrane proteins to the actin cytoskeleton, associates with ASIC1a in brain and in cultured cells. The interaction depended on an α-actinin-binding site in the ASIC1a C terminus that was specific for ASIC1a versus other ASICs and for α-actinin-1 and -4. Co-expressing α-actinin-4 altered ASIC1a current density, pH sensitivity, desensitization rate, and recovery from desensitization. Moreover, reducing α-actinin expression altered acid-activated currents in hippocampal neurons. These findings suggest that α-actinins may link ASIC1a to a macromolecular complex in the postsynaptic membrane where it regulates ASIC1a activity.Acid-sensing ion channels (ASICs)² are H⁺-gated members of the DEG/ENaC family (1–3). Members of this family contain cytosolic N and C termini, two transmembrane domains, and a large cysteine-rich extracellular domain. ASIC subunits combine as homo- or heterotrimers to form cation channels that are widely expressed in the central and peripheral nervous systems (1–4). In mammals, four genes encode ASICs, and two subunits, ASIC1 and ASIC2, have two splice forms, a and b. Central nervous system neurons express ASIC1a, ASIC2a, and ASIC2b (5–7). Homomeric ASIC1a channels are activated when extracellular pH drops below 7.2, and half-maximal activation occurs at pH 6.5–6.8 (8–10). These channels desensitize in the continued presence of a low extracellular pH, and they can conduct Ca²⁺ (9, 11–13). ASIC1a is required for acid-evoked currents in central nervous system neurons; disrupting the gene encoding ASIC1a eliminates H⁺-gated currents unless extracellular pH is reduced below pH 5.0 (5, 7).Previous studies found ASIC1a enriched in synaptosomal membrane fractions and present in dendritic spines, the site of excitatory synapses (5, 14, 15). Consistent with this localization, ASIC1a null mice manifested deficits in hippocampal long term potentiation, learning, and memory, which suggested that ASIC1a is required for normal synaptic plasticity (5, 16). ASICs might be activated during neurotransmission when synaptic vesicles empty their acidic contents into the synaptic cleft or when neuronal activity lowers extracellular pH (17–19). Ion channels, including those at the synapse often interact with multiple proteins in a macromolecular complex that incorporates regulators of their function (20, 21). For ASIC1a, only a few interacting proteins have been identified. Earlier work indicated that ASIC1a interacts with another postsynaptic scaffolding protein, PICK1 (15, 22, 23). ASIC1a also has been reported to interact with annexin II light chain p11 through its cytosolic N terminus to increase cell surface expression (24) and with Ca²⁺/calmodulin-dependent protein kinase II to phosphorylate the channel (25). However, whether ASIC1a interacts with additional proteins and with the cytoskeleton remain unknown. Moreover, it is not known whether such interactions alter ASIC1a function.In analyzing the ASIC1a amino acid sequence, we identified cytosolic residues that might bind α-actinins. α-Actinins cluster membrane proteins and signaling molecules into macromolecular complexes and link membrane proteins to the actincytoskeleton (for review, Ref. 26). Four genes encode α-actinin-1, -2, -3, and -4 isoforms. α-Actinins contain an N-terminal head domain that binds F-actin, a C-terminal region containing two EF-hand motifs, and a central rod domain containing four spectrin-like motifs (26–28). The C-terminal portion of the rod segment appears to be crucial for binding to membrane proteins. The α-actinins assemble into antiparallel homodimers through interactions in their rod domain. α-Actinins-1, -2, and -4 are enriched in dendritic spines, concentrating at the postsynaptic membrane (29–35). In the postsynaptic membrane of excitatory synapses, α-actinin connects the NMDA receptor to the actin cytoskeleton, and this interaction is key for Ca²⁺-dependent inhibition of NMDA receptors (36–38). α-Actinins can also regulate the membrane trafficking and function of several cation channels, including L-type Ca²⁺ channels, K⁺ channels, and TRP channels (39–41).To better understand the function of ASIC1a channels in macromolecular complexes, we asked if ASIC1a associates with α-actinins. We were interested in the α-actinins because they and ASIC1a, both, are present in dendritic spines, ASIC1a contains a potential α-actinin binding sequence, and the related epithelial Na⁺ channel (ENaC) interacts with the cytoskeleton (42, 43). Therefore, we hypothesized that α-actinin interacts structurally and functionally with ASIC1a.     

LigPath: a module for predictive calculation of a ligand’s pathway into a receptor-application to the gpH<Subscript>1</Subscript> - receptor

Until now, the access of ligands into the binding pocket of a G-protein coupled receptor has scarcely been studied using molecular-modeling techniques because of the lack of sufficient algorithms. Neither with Monte-Carlo- nor with Molecular Dynamics Simulations can the penetration of a ligand into the binding pocket of a receptor be calculated because of the excessive amount of computing time needed. Therefore, a new algorithm LigPath for approximate calculation of a ligand’s pathway into the binding pocket has been developed. This new algorithm is based on a linkage of directional guiding of the ligand, Monte-Carlo-Search and minimization. In order to evaluate the performance of the algorithm, the guinea-pig histamine H₁ receptor was investigated in combination with one of its potent agonists, histaprodifen, which is proposed to bind in a pocket deep between the transmembrane helices of the receptor. Our calculations show that the amino acids Tyr194, Phe193, Phe436 and Phe433 guide the positively charged histaprodifen from the extracellular part of the receptor into the binding pocket.     

<Emphasis Type="Italic">Glycine max</Emphasis> non-nodulation locus <Emphasis Type="Italic">rj1</Emphasis>: a recombinogenic region encompassing a SNP in a lysine motif receptor-like kinase (<Emphasis Type="Italic">GmNFR1α</Emphasis>)

The rj1 mutation of soybean is a simple recessive allele in a single line that arose as a spontaneous mutation in a population; it exhibits non-nodulation with virtually all Bradyrhizobium and Sinorhizobium strains. Here, we described fine genetic and physical mapping of the rj1 locus on soybean chromosome 2. The initial mapping of the rj1 locus using public markers indicated that A343.p2, a sequence-based marker that contains sequence similar to a part of the LjNFR1 gene regulating nodule formation as a member of lysin motif-type receptor-like kinase (LYK) family, maps very close to or cosegregates with the rj1 locus. The sequence of A343.p2 is 100% identical to parts of two BAC clone sequences (GM_WBb0002O19 and GM_WBb098N11) that contain three members of the LYK family. We analyzed the sequence contig (262 kbp) of the two BAC clones by resequencing and subsequent fine genetic and physical mapping. The results indicated that rj1 is located in a gene-rich region with a recombination rate of 120 kbp/cM: several fold higher than the genome average. Among the LYK genes, NFR1α is most likely the gene encoded at the Rj1 locus. The non-nodulating rj1 allele was created by a single base-pair deletion that results in a premature stop codon. Taken together, the fine genetic and physical mapping of the Rj1-residing chromosomal region, combined with the unexpected observation of a putative recombination hotspot, allowed us to demonstrate that the Rj1 locus most likely encodes the NFR1α gene.     

Interleukin‐1β: a bridge between inflammation and excitotoxicity?

Interleukin-1 (IL-1) is a proinflammatory cytokine released by many cell types that acts in both an autocrine and/or paracrine fashion. While IL-1 is best described as an important mediator of the peripheral immune response during infection and inflammation, increasing evidence implicates IL-1 signaling in the pathogenesis of several neurological disorders. The biochemical pathway(s) by which this cytokine contributes to brain injury remain(s) largely unidentified. Herein, we review the evidence that demonstrates the contribution of IL-1β to the pathogenesis of both acute and chronic neurological disorders. Further, we highlight data that leads us to propose IL-1β as the missing mechanistic link between a potential beneficial inflammatory response and detrimental glutamate excitotoxicity.     

&quot;Mushroom cloud&quot;: a giant left ventricular pseudoaneurysm after a myocardial infarction due to myocardial bridging – a case report

Left ventricular pseudoaneurysm is an uncommon complication after transmural myocardial infarction, occurring when a free wall rupture is contained by adhesions of the overlying pericardium preventing acute tamponade. In this report, an unusual case of a 61 year-old male with a giant apical left ventricular pseudoaneurysm after an unnoticed myocardial infarction is presented. On coronary angiogram myocardial bridging of the distal left anterior descending artery was judged to be the infarct related lesion. The echocardiographic diagnosis allowed for a timely surgical intervention which resulted in the patient's full recovery.     

A Defect in Zinc Finger Protein Double B-box 1a (DBB1a) Causes Abnormal Floral Development in <Emphasis Type="Italic">Arabidopsis</Emphasis>

The double B-box (DBB) type zinc finger protein has thus far been shown to be involved in photomorphegenesis in Arabidopsis thaliana. Here, we show that DBB1a is expressed in the embryo, cytolden, and flower. Misexpression of DBB1a in mutant plants resulted in abnormal numbers and patterns of floral organs. We further show that DBB1a could regulate expression of several floral homeotic genes, including APETALA 2, APETALA 3, PISTILLATA, and AGAMOUS. Interestingly, expression of the microRNA gene MiR172, which is involved in organ boundary establishment, was also misregulated in the dbb1a mutant plants. Our study identified a previously uncharacterized role of DDB1a in regulation of expression of floral homeotic genes and miR172, which is important for understanding of floral pattern formation.     

“New”‐clear functions of PDK1: Beyond a master kinase?

Activation of cytosolic phosphoinositide-3 kinase (PI-3K) signaling pathway has been well established to regulate gene expression, cell cycle, and survival by feeding signals to the nucleus. In addition, strong evidences accumulated over the past few years indicate the presence of an autonomous inositol lipid metabolism and PI-3K signaling within the nucleus. Much less, however, is known about the role and regulation of this nuclear PI-3K pathway. Components of the PI-3K signaling pathway, including PI 3-kinase and its downstream kinase Akt, have been identified at the nuclear level. Consistent with the presence of a complete PI-3K signaling pathway in the nucleus, we have recently found that phosphoinositide-dependent kinase 1 (PDK1), a kinase functioning downstream of PI-3K and upstream of Akt, is a nucleo-cytoplasmic shuttling protein. In the present review, we update our current knowledge on the regulatory mechanisms and the functional roles of PDK1 nuclear translocation. We also summarize some of the kinase-independent activities of PDK1 in cell signaling.     

Projected [<Superscript>1</Superscript>H,<Superscript>15</Superscript>N]-HMQC-[<Superscript>1</Superscript>H,<Superscript>1</Superscript>H]-NOESY for large molecular systems: application to a 121 kDa protein-DNA complex

We present a projected [¹H,¹⁵N]-HMQC-[¹H,¹H]-NOESY experiment for observation of NOE interactions between amide protons with degenerate ¹⁵N chemical shifts in large molecular systems. The projection is achieved by simultaneous evolution of the multiple quantum coherence of the nitrogen spin and the attached proton spin. In this way NOE signals can be separated from direct-correlation peaks also in spectra with low resolution by fully exploiting both ¹H and ¹⁵N frequency differences, such that sensitivity can be increased by using short maximum evolution times. The sensitivity of the experiment is not dependent on the projection angle for projections up to 45° and no additional pulses or delays are required as compared to the conventional 2D [¹H,¹⁵N]-HMQC-NOESY. The experiment provides two distinct 2D spectra corresponding to the positive and negative angle projections, respectively. With a linear combination of 1D cross-sections from the two projections the unavoidable sensitivity loss in projection spectra can be compensated for each particular NOE interaction. We demonstrate the application of the novel projection experiment for the observation of an NOE interaction between two sequential glycines with degenerate ¹⁵N chemical shifts in a 121.3 kDa complex of the linker H1 histone protein with a 152 bp linear DNA.     

Can a ‘Silent’ Person Be a ‘Business’ Person? The Concept Mãduã in Fijian Culture

The focus of the paper is an examination of the relevance of the traditional concept mãduã for an understanding of Fijian culture, particularly in the context of modern business enterprise. The concept represents a multitude of subtle as well as clearly displayed emotions and attitudes. Though mãduã is especially relevant in situations where Fijian values are centre stage, the view put forward here is that the associated expressions and bodily postures are also relevant in modern urban contexts, where perhaps one might otherwise expect them to be discarded or at least toned down. In public discourse in Fiji, where the theme of Fijian participation in both education and business is constantly commented on and discussed, a new notion is identified, namely ‘silence’. The author suggests that it may to some degree replace and encompass mãduã The prime concern of the article, however, is to bring to the fore reflections by Fijians themselves on existential dilemmas, one of which is about how to live with mãduã in the modern context.     

Polymeric Osteopontin Employs Integrin ��9��1 as a Receptor and Attracts Neutrophils by Presenting a de Novo Binding Site

Osteopontin (OPN) is a cytokine and ligand for multiple members of the integrin family. OPN undergoes the in vivo polymerization catalyzed by cross-linking enzyme transglutaminase 2, which consequently increases the bioactivity through enhanced interaction with integrins. The integrin α9β1, highly expressed on neutrophils, binds to the sequence SVVYGLR only after intact OPN is cleaved by thrombin. The SVVYGLR sequence appears to be cryptic in intact OPN because α9β1 does not recognize intact OPN. Because transglutaminase 2-catalyzed polymers change their physical and chemical properties, we hypothesized that the SVVYGLR site might also be exposed on polymeric OPN. As expected, α9β1 turned into a receptor for polymeric OPN, a result obtained by cell adhesion and migration assays with α9-transfected cells and by detection of direct binding of recombinant soluble α9β1 with colorimetry and surface plasmon resonance analysis. Because the N-terminal fragment of thrombin-cleaved OPN, a ligand for α9β1, has been reported to attract neutrophils, we next examined migration of neutrophils to polymeric OPN using time-lapse microscopy. Polymeric OPN showed potent neutrophil chemotactic activity, which was clearly inhibited by anti-α9β1 antibody. Unexpectedly, mutagenesis studies showed that α9β1 bound to polymeric OPN independently of the SVVYGLR sequence, and further, SVVYGLR sequence of polymeric OPN was cryptic because SVVYGLR-specific antibody did not recognize polymeric OPN. These results demonstrate that polymerization of OPN generates a novel α9β1-binding site and that the interaction of this site with the α9β1 integrin is critical to the neutrophil chemotaxis induced by polymeric OPN.Acidic phosphorylated secreted glycoprotein osteopontin (OPN),⁴ known as a cytokine, has multiple functions, including roles in tissue remodeling, fibrosis, mineralization, immunomodulation, inflammation, and tumor metastasis (1–3). OPN is also an integrin ligand. At least nine integrins can function as OPN receptors. α5β1, α8β1, αvβ1, αvβ3, αvβ5 (1), and αvβ6 (4) recognize the linear tripeptide RGD, and α9β1, α4β1, and α4β7 recognize the sequence, SVVYGLR (5), adjacent to RGD but only after OPN has been cleaved by the protease, thrombin (Fig. 1).Open in a separate windowFIGURE 1.Schematic diagram of OPN. Two integrin-binding sites (boxed), a thrombin cleavage site (arrow), and a putative transglutamination site (circled) are shown. The term thrombin-cleaved nOPN is defined as in the figure.The overlap of receptors for OPN does not necessarily mean that these integrins play redundant roles in cellular responses to OPN because the patterns of integrin expression and utilization vary widely among cell types. In addition, interactions of different integrins with a single ligand can exert distinct effects on cell behavior in a single cell type. For example, we have previously reported that signals by ligation of αvβ3, αvβ6, or α9β1 to a single ligand, tenascin-C, differently affected cell adhesion, spreading, and proliferation of the colon cancer cell line, SW480 (6). Furthermore, intact OPN or thrombin- or matrix metalloproteinase-cleaved OPN interact with distinct subsets of integrins and exhibit distinct effects on cell behavior (4, 7, 8). Collectively, some of the functional diversity of OPN could be attributed to this multiplicity of receptors and responses. We have recently shown that polymerization of OPN results in enhanced biological activity (9). We thus set out to determine whether polymerized OPN exerts its effects through unique interactions with integrins.OPN is polymerized by transglutaminase 2 (TG2, EC 2.3.2.13) (10) that catalyzes formation of isopeptide cross-links between glutamine and lysine residues in substrate proteins (11) including OPN. Polymeric OPN has been identified in vivo in bone (12) and calcified aorta (13). We have previously reported that upon polymerization, OPN displays increased integrin binding accompanied by enhanced cell adhesion, spreading, migration, and focal contact formation (9). However, very little is known about how polymeric OPN induces its biological effects.Integrin α9β1, highly expressed on neutrophils (14), does not act as a receptor for intact OPN but does bind to an N-terminal fragment of OPN (nOPN) that is generated by thrombin cleavage (15) through the new C-terminal sequence, SVVYGLR. Protein polymerization can expose otherwise cryptic domains (16), so we hypothesized that the SVVYGLR site might be exposed upon polymerization and serve as a binding site for α9β1. In the present study, we demonstrate that α9β1 is indeed a receptor for polymeric OPN and that neutrophil migration induced by polymeric OPN is largely mediated by this interaction. However, mutational analysis and antibody studies demonstrate that this interaction does not involve the SVVYGLR site, suggesting the presence of de novo binding site in polymeric OPN.     

The<Emphasis Type="Italic"> diageotropica</Emphasis> mutation of tomato disrupts a signalling chain using extracellular auxin binding protein 1 as a receptor

The diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) is known to lack a number of typical auxin responses. Here we show that rapid auxin-induced growth of seedling hypocotyls is completely abolished by the mutation over the full range of auxin concentrations tested, and also in early phases of the time course. Protoplasts isolated from wild-type hypocotyls respond to auxin by a rapid increase in cell volume, which we measured by image analysis at a high temporal resolution. A similar swelling could be triggered by antibodies directed against a part of the putative auxin-binding domain (box-a) of the auxin-binding protein 1 (ABP1). Induction of swelling both by auxin and by the antibody was not observed in the protoplasts isolated from the dgt mutant. However, dgt protoplasts are able to respond to the stimulator of the H⁺-ATPase, fusicoccin, with normal swelling. We propose that dgt is a signal-transduction mutation interfering with an auxin-signalling pathway that uses ABP1 as a receptor.Abbreviations ABP auxin-binding protein - CCD charge-coupled device - 2,4-D 2,4-dichlorophenoxyacetic acid - dgt diageotropica - FC fusicoccin     

Identification of a Novel Bacterial Outer Membrane Interleukin-1Β-Binding Protein from Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans is a gram-negative opportunistic oral pathogen. It is frequently associated with subgingival biofilms of both chronic and aggressive periodontitis, and the diseased sites of the periodontium exhibit increased levels of the proinflammatory mediator interleukin (IL)-1β. Some bacterial species can alter their physiological properties as a result of sensing IL-1β. We have recently shown that this cytokine localizes to the cytoplasm of A. actinomycetemcomitans in co-cultures with organotypic gingival mucosa. However, current knowledge about the mechanism underlying bacterial IL-1β sensing is still limited. In this study, we characterized the interaction of A. actinomycetemcomitans total membrane protein with IL-1β through electrophoretic mobility shift assays. The interacting protein, which we have designated bacterial interleukin receptor I (BilRI), was identified through mass spectrometry and was found to be Pasteurellaceae specific. Based on the results obtained using protein function prediction tools, this protein localizes to the outer membrane and contains a typical lipoprotein signal sequence. All six tested biofilm cultures of clinical A. actinomycetemcomitans strains expressed the protein according to phage display-derived antibody detection. Moreover, proteinase K treatment of whole A. actinomycetemcomitans cells eliminated BilRI forms that were outer membrane specific, as determined through immunoblotting. The protein was overexpressed in Escherichia coli in both the outer membrane-associated form and a soluble cytoplasmic form. When assessed using flow cytometry, the BilRI-overexpressing E. coli cells were observed to bind 2.5 times more biotinylated-IL-1β than the control cells, as detected with avidin-FITC. Overexpression of BilRI did not cause binding of a biotinylated negative control protein. In a microplate assay, soluble BilRI bound to IL-1β, but this binding was not specific, as a control protein for IL-1β also interacted with BilRI. Our findings suggest that A. actinomycetemcomitans expresses an IL-1β-binding surface-exposed lipoprotein that may be part of the bacterial IL-1β-sensing system.     

Cloning and functional analysis of chicory root fructan1‐exohydrolase I (1‐FEH I): a vacuolar enzyme derivedfrom a cell‐wall invertase ancestor? Mass fingerprint of the 1‐FEH I enzyme

This paper describes the cloning and functional analysis of chicory (Cichorium intybus L.) fructan 1-exohydrolase I cDNA (1-FEH I). To our knowledge it is the first plant FEH cloned. Full-length cDNA was obtained by a combination of RT-PCR, 5' and 3' RACE using primers based on N-terminal and conserved amino acid sequences. Electrophoretically purified 1-FEH I enzyme was further analyzed by in-gel trypsin digestion followed by matrix-assisted laser desorption ionization and electrospray time-of-flight tandem mass spectrometry. Functionality of the cDNA was demonstrated by heterologous expression in potato tubers. 1-FEH I takes a new, distinct position in the phylogenetic tree of plant glycosyl hydrolases being more homologous to cell-wall invertases (44-53%) than to vacuolar invertases (38-41%) and fructosyl transferases (33-38%). The 1-FEH I enzyme could not be purified from the apoplastic fluid at significantly higher levels than can be explained by cellular leakage. These and other data suggest a vacuolar localization for 1-FEH I. Also, the pI of the enzyme (6.5) is lower than expected from a typical cell-wall invertase. Unlike plant fructosyl transferases that are believed to have evolved from a vacuolar invertase, 1-FEH I might have evolved from a cell-wall invertase-like ancestor gene that later obtained a vacuolar targeting signal. 1-FEH I mRNA quantities increase in the roots throughout autumn, and especially when roots are stored at low temperature.     

Does a polymorphic species have a ‘polymorphic’ diet? A case study from a lacertid lizard

Lizards are ideal for studying colour polymorphism, because some species are polymorphic and the morphs often have different ecological or reproductive strategies. We studied the feeding habits of six polymorphic populations of Podarcis muralis to test whether morphs differed in their diet. Some taxa were selected in a similar way by all morphs, but selection on other taxa varied and was characteristic of each morph. Diet was most different for the red and yellow morphs. Two hypotheses could explain these differences: active segregation in the trophic niche or active segregation in space dependent on spatial heterogeneity in prey availability. The former is improbable because P. muralis is considered an opportunistic feeder, whereas the latter could occur if the morphs adopted alternative territorial strategies with consequent spatial segregation.     

Bergmann's rule; a concept cluster?

The science behind ecology has been contested for years, partially because of the misuse and misrepresentation of concepts within ecology. This paper discusses the use of Bergmann's rule, a fundamental rule of biogeography. The rule was proposed by Carl Bergmann in 1847 and was published only in German; therefore, the majority of researchers have relied on a single translation by Mayr suggesting that races from cooler climates tend to be larger in species of warm-blooded vertebrates than races of the same species living in warmer climates. That many scientists cannot go back to the original source of information because it has not been published in English has resulted in relying on others for interpretation and led to several problems, the largest of which is whether the definition of the rule should include the mechanism, which had been proposed by Bergmann. There has been a large field of research on the subject, but few tests of the mechanisms behind the observed phenomenon. We conducted a review of the literature on Bergmann's rule, and from this suggest (1) Bergmann's original rule be maintained (a direct translation is provided), (2) mechanism is inherent in Bergmann's rule and is required for a rule to be of scientific value; patterns should be labelled as trends, not rules, (3) the focus should be on falsifying hypothesized mechanisms rather than simply describing patterns, and (4) to truly evaluate Bergmann's rule in a scientific manner the original German source should be translated and made available to the scientific public.     

Characterization of a NaCl-tolerant β-N-acetylglucosaminidase from <Emphasis Type="Italic">Sphingobacterium</Emphasis> sp. HWLB1

β-N-Acetylglucosaminidases serve important biological functions and various industrial applications. A glycoside hydrolase family 3 β-N-acetylglucosaminidase gene was cloned from Sphingobacterium sp. HWLB1 and expressed in Escherichia coli BL21 (DE3). The purified recombinant enzyme (rNag3HWLB1) showed apparent optimal activity at pH 7.0 and 40 °C. In the presence of 0.5–20.0 % (w/v) NaCl, the activity and stability of rNag3HWLB1 were slightly affected or not affected. The enzyme could even retain 73.6 % activity when 30.0 % (w/v) NaCl was added to the reaction mixture. The half-life of the enzyme was approximately 10 min at 37 °C without the addition of NaCl. However, the enzyme was stable at 37 °C in the presence of 3.0 % (w/v) NaCl. A large negatively charged surface in the catalytic pocket of the enzyme was observed and might contribute to NaCl tolerance and thermostability improvement. The degree of synergy between a commercial endochitinase and rNag3HWLB1 on chitin enzymatic degradation ranged from 3.11 to 3.74. This study is the first to report the molecular and biochemical properties of a NaCl-tolerant β-N-acetylglucosaminidase.