Sugars often receive simplistic treatment as mere energy sources, but β-1,2-glucans reveal the far more nuanced roles carbohydrates can play. These polysaccharides, with recurring glucose units linked by β-1,2 glycosidic bonds, are pivotal in mediating inter-organismal interactions. Their presence spans diverse bacterial and plant species, where they contribute to survival strategies, host infections, and mutually beneficial symbioses. For instance, Brucella abortus, a zoonotic pathogen, employs cyclic β-1,2-glucans to subvert host immune defenses, facilitating bacterial persistence inside immune cells. Meanwhile, Xanthomonas species manipulate similar glucans to colonize and infect plants like Arabidopsis thaliana and Nicotiana benthamiana, highlighting the versatile roles of these molecules.

Despite burgeoning interest in the enzymology of β-1,2-glucan metabolism, the specific pathways enabling their transport across bacterial membranes have remained stubbornly obscure. Transport is a critical bottleneck; without efficient import/export, extracellular β-1,2-glucans cannot serve as viable nutrient sources or signaling molecules. Limited existing data portray these bacterial transport systems as heterogenous, implying extensive undiscovered diversity and raising the tantalizing possibility of novel molecular architectures.

The team led by Associate Professor Masahiro Nakajima and Professor Hidetaka Torigoe capitalized on this knowledge gap by focusing their investigation on Chy400_4166, a putative solute-binding protein within an ABC transporter operon in C. aurantiacus. ABC transporters are ATP-driven molecular machines that ferry specific substrates across membranes with high affinity and selectivity. Chy400_4166’s proximity to β-1,2-glucan-associated genes suggested a role in glucan binding or recognition, making it a prime candidate for structural and functional characterization.

Initial biochemical assays employed gel shift electrophoresis to confirm Chy400_4166’s ability to bind β-1,2-glucans. Building upon this, isothermal titration calorimetry (ITC) quantified binding affinities for a range of linear and cyclic β-1,2-glucan substrates, revealing not only selectivity but also fine-tuned thermodynamic properties indicative of a highly specialized interaction. These quantitative assays set the stage for the central breakthrough: atomic-resolution crystal structures determined via X-ray crystallography, providing exquisite detail of the protein-saccharide interface.

The crystalline snapshots illuminated a compelling binding mode, with Chy400_4166 engaging ten consecutive glucose units in β-1,2 linkage to establish a shared core interface. Notably, a single glucose unit, designated as unit G, was firmly anchored by conserved amino acids, underscoring its importance as a structural lynchpin. This binding modality contrasts sharply with previously characterized β-1,2-glucan binding proteins, such as the one from Listeria innocua, which target terminal sugar units. Instead, Chy400_4166’s affinity centers on an internal segment of longer glucan chains, optimizing interactions with cyclic forms of β-1,2-glucans that predominate in vivo.

The protein’s architecture reveals a remarkable degree of conformational flexibility, especially in key residues capable of adopting multiple positions to accommodate glucans of varying ring sizes. This adaptability likely underlies the protein’s ability to bind diverse β-1,2-glucan substrates efficiently, a feature that might be evolutionarily tuned to environmental variability. Dr. Nakajima emphasized these findings as emblematic of the unexpected functional diversity among β-1,2-glucan binding proteins, suggesting a rich landscape of molecular adaptations in microbial sugar transport.

These insights carry significant implications beyond fundamental microbiology. Since cyclic β-1,2-glucans represent virulence factors for various pathogens, proteins like Chy400_4166 could be exploited as molecular targets to disrupt pathogenic infection cycles. The competitive administration of cyclic β-1,2-glucans to susceptible plants might effectively block microbial colonization, offering a promising strategy for biological crop protection. Such an approach would reduce reliance on synthetic pesticides, aligning with sustainable agriculture initiatives.

Furthermore, cyclic β-1,2-glucans possess unique structural features allowing them to encapsulate other molecules within their rings. The elucidated transport system may thus serve as a conceptual framework for engineering novel drug delivery vehicles, leveraging glucan encapsulation to shuttle therapeutics with precision. This biochemical toolkit also holds promise for environmental biotechnology applications and food science, where controlled transport and modification of such polysaccharides can enhance bioproduct development.

The study’s comprehensive integration of thermodynamics, structural biology, and microbial ecology exemplifies how multidisciplinary approaches can unravel the complexities of molecular transport systems. As researchers continue to map the diversity of ABC transporters and their substrate-binding partners, new layers of bacterial adaptation and survival strategies are expected to emerge, broadening our grasp of microbial life and its manipulation.

Associate Professor Nakajima concluded by underscoring the broader goal of illuminating glycans—biomolecules often overshadowed by nucleic acids and proteins. The discovery of this novel β-1,2-glucan transport system marks a pivotal step toward appreciating the ecological ubiquity and biological importance of these sugars, opening fertile ground for future research and practical innovation.

This pioneering work exemplifies the power of combining structural and thermodynamic analyses to decode the nuanced molecular interplay governing bacterial physiology. As more β-1,2-glucan-associated proteins are characterized, we are poised to uncover novel molecular mechanisms, therapeutic opportunities, and biotechnological applications that leverage the subtle but critical roles of these complex carbohydrates.

The full research can be accessed via DOI 10.1111/febs.70576, published May 10, 2026, marking a vibrant addition to the expanding vista of glycobiology and microbial transport systems.

Subject of Research: Cells

Article Title: Structural and thermodynamic analyses of a novel β-1,2-glucan binding mode in the ABC transporter solute-binding protein Chy400_4166 from Chloroflexus aurantiacus

News Publication Date: 10-May-2026

Web References: http://dx.doi.org/10.1111/febs.70576

References: Kazuya Kato, Tatsuya Kaneko, Rintaro Hirayama, Nobukiyo Tanaka, Hiroyuki Nakai, Hidetaka Torigoe, and Masahiro Nakajima, The FEBS Journal, 2026.

Image Credits: Associate Professor Masahiro Nakajima and Professor Hidetaka Torigoe, Tokyo University of Science, Japan

Keywords: β-1,2-glucan, ABC transporter, solute-binding protein, Chy400_4166, bacterial sugar transport, structural biology, thermodynamics, cyclic glucans, molecular flexibility, plant pathogens, microbial interactions, glycobiology

A recent breakthrough study, published in Nature and conducted by the collaborative efforts of Duke University’s renowned biochemists Seok-Yong Lee, PhD, and Kenichi Yokoyama, PhD, now unveils the intricate molecular choreography that governs caspofungin’s function. This pivotal investigation not only delineates the drug’s binding interactions in unprecedented atomic detail, but also elucidates the enigmatic biochemical basis for emerging drug resistance. By exposing the true mechanism, it lays a critical foundation for designing next-generation antifungals capable of outpacing fungal adaptation and resistance.

Prior paradigms posited a relatively straightforward interaction: caspofungin was believed to directly inhibit the fungal enzyme β-1,3-D-glucan synthase, which is indispensable for the biosynthesis of β-1,3-glucan—a vital glucan polymer that constitutes the structural scaffold of the fungal cell wall. This inhibition was assumed to impede the enzyme’s catalytic function directly, effectively halting cell wall assembly. However, the Duke research team’s meticulous structural and biochemical analyses disrupt this simplistic narrative, revealing a far more sophisticated mode of inhibition.

Contrary to earlier assumptions, caspofungin does not bind solely to the enzyme’s active site in isolation. Instead, it forms a ternary complex that simultaneously engages the enzyme, the nascent β-1,3-glucan polymer elongating from the enzyme, and the drug molecule itself. This tripartite interaction effectively “traps” the growing glucan chain inside the enzyme complex, jamming the biosynthetic machinery mid-synthesis. As a result, the enzyme becomes arrested in a catalytically inactive state, unable to incorporate additional glucan subunits. This molecular blockade stalls cell wall construction, critically compromising fungal viability.

This nuanced understanding has far-reaching implications for antifungal pharmacology. The discovery clarifies why certain point mutations in the glucan synthase enzyme’s structure confer resistance: they likely disrupt the formation or stability of the drug-enzyme-glucan complex, allowing enzymatic activity to persist despite drug presence. Moreover, this model provides a plausible explanation for clinical cases wherein caspofungin therapy has failed, despite satisfactory dosing and administration.

Achieving this breakthrough required surmounting formidable experimental obstacles, particularly capturing β-1,3-D-glucan synthase in its active, substrate-processing state. The enzyme is notoriously challenging to study due to its highly dynamic nature and membrane-bound complexities. The Duke team innovatively combined advanced enzymology with state-of-the-art cryo-electron microscopy (cryo-EM), synchronizing enzymatic activity with high-resolution structural imaging. This approach permitted visualization of the enzyme during glucan polymerization, revealing the real-time binding interactions of caspofungin.

The cryo-EM images obtained afforded an atomic-level snapshot of the enzyme-drug-substrate interface. They demonstrated that caspofungin’s binding affinity manifests only when β-1,3-D-glucan synthase is actively elongating the glucan chain; in its inactive or resting states, the enzyme exhibits negligible drug binding. This insight is critical, highlighting the necessity of preserving enzymatic functionality during structural interrogation to uncover relevant pharmacological interactions.

Dr. Lee emphasized that these structural revelations were indispensable for understanding the drug’s mechanism of action at a molecular level, stating that “the images show exactly how caspofungin interacts with the enzyme and the glucan it produces.” This detailed knowledge could spearhead rational drug design, steering medicinal chemistry toward compounds optimized to stabilize or mimic this inhibitory ternary complex, thereby enhancing efficacy and circumventing resistance.

Given the escalating global burden of invasive fungal diseases and the comparative paucity of novel antifungal agents in the development pipeline, these findings arrive at a pivotal moment. They invigorate the antifungal research community and pharmaceutical industry with mechanistic targets for next-generation therapeutics designed to outmaneuver adaptive fungal pathogens.

Furthermore, the study underscores the vital importance of integrating multidisciplinary expertise—including structural biology, enzymology, and pharmacology—in tackling complex antimicrobial resistance challenges. The Duke University collaboration exemplifies how such synergy can break longstanding impasses in biomedical research, delivering insights that extend well beyond caspofungin to broader antifungal strategies and potentially other classes of antimicrobial agents.

Ultimately, this work not only deepens fundamental understanding of fungal cell wall biosynthesis and its pharmacological inhibition but also charts a promising path to renewed therapeutic innovation. As fungal diseases continue to threaten vulnerable populations worldwide, strategic exploitation of these molecular insights will be essential to safeguard public health and combat future outbreaks with more effective and durable antifungal treatments.

Subject of Research: Not applicable

Article Title: Structural basis of fungal β−1,3-glucan synthase inhibition by caspofungin

News Publication Date: 22-Apr-2026

Web References: http://dx.doi.org/10.1038/s41586-026-10409-7

Image Credits: Duke University

Keywords: Antifungal agents, Biochemistry

Fungal pathogens, including species such as Candida, Aspergillus, and Cryptococcus, rely heavily on the structural integrity of their cell walls for survival and pathogenicity. The β-1,3-glucan synthase enzyme complex is essential in biosynthesizing β-1,3-glucan polymers, which form the backbone of the fungal cell wall. Traditional antifungal agents have often targeted these enzymes indirectly or faced limitations due to toxicity and emerging resistance. However, triterpenoid antifungal drugs, a class of naturally derived molecules, have recently gained attention for their potent activity and unique mode of action, as elucidated by the research team.

Employing a multidisciplinary approach integrating cryo-electron microscopy (cryo-EM), biochemical assays, and molecular dynamics simulations, the researchers obtained high-resolution structures of β-1,3-glucan synthase in complex with representative triterpenoid molecules. This allowed them to pinpoint the precise binding sites and characterize conformational changes induced upon drug binding. The data revealed that triterpenoids exert their inhibitory effect by locking the enzyme in an inactive conformation that prevents the translocation of the growing glucan chain, effectively halting cell wall synthesis at a critical stage.

The structural insights gleaned from this study elucidate how triterpenoids exploit a previously unidentified allosteric pocket on the catalytic subunit of β-1,3-glucan synthase. This binding site is distinct from the active site responsible for substrate polymerization, indicating a novel mechanism of inhibition that circumvents the enzyme’s natural catalytic activity. By stabilizing this inactive conformation, triterpenoid drugs induce a dominant-negative effect, diminishing enzyme kinetics and thereby crippling fungal cell wall assembly.

Understanding the precise molecular interactions that underlie triterpenoid binding revealed critical residues involved in hydrophobic interactions and hydrogen bonding networks, shedding light on structure-activity relationships that can inform rational drug design. The researchers demonstrated that subtle modifications of the triterpenoid scaffold can enhance affinity and selectivity toward fungal β-1,3-glucan synthases while minimizing off-target toxicity to human cells.

The implications of this discovery extend beyond molecular pharmacology into clinical realms. Fungal infections, especially in immunocompromised patients, are notoriously difficult to treat due to limited drug options and increasing resistance. The detailed mechanism of triterpenoid inhibition provides a blueprint for developing next-generation antifungal agents with improved efficacy and reduced susceptibility to resistance mechanisms, potentially revolutionizing therapeutic approaches.

Moreover, these findings underscore the potential of targeting allosteric sites as a strategic avenue in antifungal drug discovery, complementing the prevailing active site-directed approaches that dominate current pharmacotherapy. Allosteric inhibition offers advantages such as reduced likelihood of resistance development and greater specificity, characteristics essential for combating persistent fungal pathogens.

The study also delved into comparative analyses of fungal and mammalian homologs of glucan synthase enzymes, highlighting the evolutionary divergence of the identified allosteric pocket. This specificity adds a therapeutic window for selective targeting, reducing the risk of adverse effects posed by cross-reactivity with human enzymes, a persistent hurdle in antifungal drug development.

Notably, the research team conducted in vitro and in vivo efficacy tests that confirmed the potent antifungal activity of the triterpenoid compounds identified, coupled with favorable pharmacokinetic properties. Animal models of invasive fungal infections treated with these compounds exhibited significantly improved survival rates and reduced fungal burden, demonstrating translational potential.

The comprehensive characterization of these triterpenoid inhibitors also revealed resistance profiles, indicating low frequencies of resistance mutations emerging within fungal populations. The mutations identified localized primarily to residues in the allosteric pocket, hinting at a potential evolutionary restraint, which further supports the durability of triterpenoid-based therapies in clinical applications.

Beyond therapeutic implications, this work enhances our fundamental understanding of fungal biology and enzymology. The β-1,3-glucan synthase complex is a challenging target due to its size, membrane association, and dynamic nature. The application of cutting-edge structural biology techniques enabled by this research overcomes these obstacles, offering a paradigm for studying other critical membrane-bound enzymatic complexes.

Additionally, the molecular dynamics simulations presented illustrate how triterpenoid binding affects local membrane environments, influencing enzyme stability and function. Such insights emphasize the complexity of drug-enzyme interactions within the lipid bilayer context and open new vistas for modulating membrane-bound targets in infectious diseases.

As fungal pathogens continue to adapt and evade conventional treatments, this pioneering work signals a transformative moment in antifungal drug discovery. By unraveling the inhibition mechanism of β-1,3-glucan synthases at atomic resolution, the study illuminates a promising path toward safer, more effective antifungal therapies that leverage nature’s own chemical arsenal.

This research also raises intriguing questions about the evolutionary pressures shaping fungal cell wall biosynthesis and the potential co-evolution of natural antifungal compounds like triterpenoids. Future studies building upon these findings may explore synthetic and biosynthetic engineering of triterpenoids to further enhance their therapeutic indices and expand their antifungal spectrums.

Ultimately, the synergy between chemical biology, structural enzymology, and pharmacology demonstrated here exemplifies the power of interdisciplinary science in addressing urgent biomedical challenges. As triterpenoid inhibitors enter preclinical and clinical development, their impact on global fungal disease management could be profound, reducing morbidity and mortality associated with fungal infections worldwide.

The team’s innovative approach and detailed mechanistic insights stand as a testament to the relentless quest for knowledge that fuels scientific progress. This landmark study not only advances our understanding of vital fungal enzymes but also inspires the design of novel antifungal agents capable of overcoming the daunting challenges posed by fungal pathogens.

Subject of Research: The inhibition mechanism of fungal β-1,3-glucan synthases by triterpenoid antifungal drugs.

Article Title: Inhibition mechanism of the fungal β−1,3-glucan synthases by triterpenoid antifungal drugs.

Article References:
You, ZL., Sun, L., Wang, LX. et al. Inhibition mechanism of the fungal β−1,3-glucan synthases by triterpenoid antifungal drugs. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69114-8

Image Credits: AI Generated

Carbohydrates are fundamental biomolecules indispensable for life, serving both as crucial energy reservoirs and structural components across all domains of life. Among sugars, β-1,2-glucans occupy a unique niche. These glucose-based polysaccharides are predominantly bacterial in origin and are involved in myriad physiological functions including bacterial pathogenicity and adaptability to environmental pressures. Despite their significance, studying β-1,2-glucans has been challenging due to their relative scarcity and highly intricate structural arrangements, which stand in contrast to more commonly studied polysaccharides like cellulose.

The TUS research team, led by Associate Professor Masahiro Nakajima, embarked on an ambitious project to uncover new glycoside hydrolase (GH) enzymes capable of degrading these elusive β-1,2-glucans. Their approach combined in-depth sequence analyses, biochemical characterization, structural elucidation, and phylogenetic investigations, targeting a cluster of previously unclassified GH enzymes suspected of being related to known β-1,2-glucanases within GH families 144 and 162. This multifaceted methodological framework allowed the team to identify new enzyme families exhibiting β-1,2-glucanase activity, marking a considerable leap forward in carbohydrate enzymology.

Central to their findings was the identification of four novel glycoside hydrolase families, three of which demonstrated enzymatic activity consistent with β-1,2-glucan degradation. Despite exhibiting as low as 16–20% amino acid sequence similarity among themselves, these enzymes were unified by shared structural motifs, most notably the (α/α)6-barrel fold, a feature previously identified in certain glycosidases. Furthermore, these new enzymes exhibited an identical anomer-inverting hydrolytic mechanism — a fundamental catalytic strategy whereby the stereochemistry at the anomeric carbon is inverted during glycosidic bond cleavage.

Such structural and mechanistic congruencies led the research team to propose the formation of a new classification, termed the “SGL clan,” encompassing three freshly characterized families GH192, GH193, GH194 alongside the established GH144 and GH162 families. Intriguingly, the GH189 family, which employs an anomer-retaining catalytic mechanism, was also included within this clan owing to phylogenetic relations and functional characteristics. This clan-based classification not only groups sharing evolutionary traits but also emphasizes the remarkable molecular diversity underscored by their catalytic features.

One of the most compelling aspects of this study lies in the molecular evolution of these enzymes. The researchers demonstrated that the irregular distribution of catalytic reaction mechanisms across the SGL clan correlates phylogenetically to variations in the positions of key catalytic residues. This suggests a unique evolutionary trajectory, through which substrate specificity and enzymatic mechanisms diversified from common ancestors. Despite their functions converging on β-1,2-glucan cleavage, these enzymes share only three strictly conserved amino acid residues—E239, Y367, and F286—which the authors identify as the defining molecular signature of the SGL clan.

This focused conservation amidst widespread sequence divergence highlights an evolutionary strategy that balances functional conservation with sequence diversification. It also provides a powerful molecular marker to identify and classify new β-1,2-glucanases within this clan, potentially accelerating the discovery of additional enzymes with related functions but novel sequences.

The study’s implications extend far beyond taxonomy and enzymology. Glycans are notoriously complex, and their structural diversity makes their enzymatic synthesis and degradation a technically demanding endeavor. By unraveling the molecular underpinnings of β-1,2-glucanase activity and expanding the repertoire of enzymes capable of mediating these reactions, the research opens new pathways for engineering synthetic and degradative enzymes. Such progress has transformative potential for diverse applications, including the tailored synthesis of oligosaccharides for therapeutic use, improved understanding of bacterial virulence mechanisms, and novel biotechnological tools for sustainable biofuel production.

Importantly, this research exemplifies the dynamic interplay between glycan synthesis and degradation. As Dr. Nakajima notes, the synergistic exploration of both enzymatic synthesis and degradation significantly expands our comprehension of glycan biology. Not only do these enzymes have roles in catabolism, but they also bear the potential for engineered synthetic applications where modifying enzyme specificity and function could yield custom-designed oligosaccharides — molecules critical for pharmaceuticals, diagnostics, and beyond.

The interdisciplinary collaboration that fueled these discoveries deserves recognition. Dr. Nakajima’s leadership, supported by contributions from former doctoral student Dr. Sei Motouchi, Associate Professor Hiroyuki Nakai from Niigata University, and Dr. Kaito Kobayashi from the National Institute of Advanced Industrial Science and Technology, represented a collaborative synergy that leveraged expertise spanning structural biology, enzymology, and phylogenetics. Their integrated approach exemplifies how cross-institutional collaboration can accelerate innovation in glycobiology research.

Furthermore, the revelation that the evolutionary distribution of enzyme catalytic mechanisms is tightly linked to the spatial organization of essential residues adds a new layer of understanding to how enzymatic function evolves. This knowledge facilitates rational enzyme engineering, allowing scientists to anticipate how modifications in residue positioning might shift reaction stereochemistry or substrate specificity, paving the way for customized enzyme design.

From a broader perspective, uncovering the molecular evolution pathways of these enzymes enriches the ever-growing catalogue of carbohydrate-active enzymes (CAZymes), a group crucial to biotechnology and life sciences. This sophisticated understanding of SGL clan enzymes highlights the evolutionary adaptability of bacteria and indicates potential targets for antibiotic development, given the role of β-1,2-glucans in bacterial physiology and pathogenicity.

In conclusion, the identification and characterization of new glycoside hydrolase families within the SGL clan deeply enrich our understanding of carbohydrate enzymology. This study not only expands the known diversity of β-1,2-glucan-degrading enzymes but also offers fresh mechanistic insights and evolutionary context that could transform future research and industrial applications. The newly proposed clan classification harmonizes complex biochemical and phylogenetic data into a cohesive framework, setting the stage for novel explorations in synthetic carbohydrate chemistry, microbial biology, and enzyme engineering.

As advances continue, the possibility of converting naturally degradative enzymes into synthetic catalysts to design novel oligosaccharides may soon become a practical reality. This would mark a paradigm shift in carbohydrate science, with wide-reaching implications for medicine, agriculture, and renewable bio-based industries. The discovery of the SGL clan thus stands as a testament to the power of interdisciplinary research to unveil nature’s molecular innovations and inspire next-generation biotechnologies.

Subject of Research: Not applicable

Article Title: New glycoside hydrolase families of β-1,2-glucanases

News Publication Date: 24-May-2025

Web References:
https://doi.org/10.1002/PRO.70147

References:
Nakajima, M., Tanaka, N., Motouchi, S., Kobayashi, K., Shimizu, H., Abe, K., Hosoyamada, N., Abara, N., Morimoto, N., Hiramoto, N., Nakata, R., Takashima, A., Hosoki, M., Suzuki, S., Shikano, K., Fujimaru, T., Imagawa, S., Kawadai, Y., Wang, Z., Kitano, Y., Nihira, T., Nakai, H., Taguchi, H. (2025). New glycoside hydrolase families of β-1,2-glucanases. Protein Science, 34(6). https://doi.org/10.1002/PRO.70147

Image Credits: Associate Professor Masahiro Nakajima, Tokyo University of Science, Japan

Keywords: β-1,2-glucanase, glycoside hydrolase, enzyme evolution, carbohydrate metabolism, glycan degradation, SGL clan, enzyme classification, molecular enzymology, phylogenetic analysis, structural biology, enzyme engineering, carbohydrate-active enzymes