TL;DR
It is shown that GeoA cargo loading is mediated by repeating, short cargo loading peptides (CLPs), and that GeoA encapsulation provides benefits for enzyme activity and stability, and provides insights into a putative mode of cargo protein regulation via pore state modulation.
Bacterial microcompartments (BMCs) are prokaryotic organelles composed of a quasi-icosahedral or polyhedral protein shell enclosing an enzymatic core. These encapsulated enzymatic cores perform coordinated metabolic functions, such as carbon fixation in carboxysomes and the catabolism of various substrates-including ethanolamine, propanediol, glycerol, choline, rhamnose, and fucose-in metabolosomes. While enzyme interaction networks within carboxysome cores are well characterized, those of metabolosomes remain comparatively understudied. Short, often amphipathic sequences known as encapsulation peptides (EPs) have been shown to mediate enzyme-shell interactions; however, their role in enzyme-enzyme (core-core) interactions is still poorly understood. In this study, we systematically and comparatively investigated EP-mediated interactions in five distinct, previously underexplored types of glycyl radical enzyme-associated (GRM) BMCs. We identified eleven novel core-core interactions and one shell-core interaction across these five GRM BMC types, with EPs being either fully or partially responsible for mediating interactions between core enzymes. These findings provide new insights into the mechanisms underlying BMC core assembly and might be useful for further biotechnological applications.
It is shown that cellulosomal principles can operate in highly reduced cohesin‐dockerin systems, and two additional candidate interacting partners for ClcC appear to bind via a non‐canonical interface.
A new class of fungal biosurfactant proteins is introduced and a simplified downstream process based on methanol/chloroform extraction is developed, reducing costs while preserving functionality.
Bacteria employ specialized metabolites called siderophores to acquire scarce iron, but these molecules may serve additional ecological roles. Here, we reveal that Pandoraea species, including environmental isolates and opportunistic pathogens typically acquired from the environment, produce bifunctional lipopeptides that undergo enzymatic remodeling to switch from promoting bacterial motility to optimizing iron capture. Through genome mining and metabolic profiling, we discovered pandorachelins, diazeniumdiolate-containing siderophores. Comprehensive NMR analysis, derivatization, and isotope labeling established that pandorachelin A is a head-to-tail-fused homodetic cyclopeptide, revising a recently proposed structure. We identified the elusive biosynthetic precursor, pandorachelin B, as a lipocyclopeptide with a lactone moiety and N-terminal fatty acid. A specialized acylase (PdnM) cleaves the lipid tail of pandorachelin B, triggering an O→N acyl shift that contracts the ring and transforms the biological function: the lipopeptide enables bacterial swarming through surfactant activity, while the delipidated product exhibits enhanced iron-chelating capacity but no motility promotion. Genetic knockouts, enzyme reconstitution, and phenotypic assays confirm this maturation sequence. The functional switch correlates with ecological niche across Pandoraea species, revealing a sophisticated strategy for niche colonization and nutrient acquisition. These findings identify PdnM as a potential antivirulence target and expand the functional repertoire of bacterial siderophores.
Abstract Fungal iterative type I polyketide synthases (iPKSs) generate structurally diverse natural products. A subset of these assembly line enzymes, exemplified by LovB from Aspergillus terreus, contains a C-terminal condensation domain bearing a noncanonical HRxxxDG motif. While these LovB-like iPKSs are widely distributed in fungi, the majority remain uncharacterized, leaving both their associated polyketide products and the function of their unusual condensation domains largely unexplored. Here, we report the characterization of a LovB-like iPKS from Aspergillus clavatus. Heterologous reconstitution of this PKS system in Aspergillus nidulans led to the discovery of clavaic acid, a previously undescribed polyketide featuring a trimethylated trans-decalin core and an all-E-configured carboxytriene side chain. Functional analysis of the condensation domain in vivo demonstrated that it is essential for clavaic acid biosynthesis. Surprisingly, whereas the conserved arginine residue within the HRxxxDG motif was dispensable for product formation, the conserved aspartate residue was strictly required. These findings expand our understanding of LovB-like iPKSs and establish this enzyme family as a promising source of cryptic fungal polyketides. One-sentence summary Genome-guided discovery of a trans-decalin-containing polyketide encoded by a LovB-like polyketide synthase in Aspergillus clavatus.
Covering: primarily from 2011 to 2026Terpenoids are an ancient and immensely diverse class of natural products. Since their emergence more than two billion years ago alongside early biological membranes, terpenoid metabolism has undergone a vast expansion in both structure and function, which directly contributed to the ecological success of terrestrial plants. Biosynthetically derived from two isomeric five-carbon isoprenoid precursors, plant terpenoids include hemi-, mono-, sesqui-, di-, sester-, tri-, tetra-, and poly-, and mero-terpenoids, that exhibit extensive variation in chain length, structural scaffolds, and functional decoration. This large chemical space is generated via dynamic metabolic networks, in which functionally versatile enzymes - most notably scaffold-forming terpene synthases and tailoring cytochrome P450 monooxygenases - are assembled into combinatorial pathway modules to yield complex bioactive terpenoid structures. Lineage-specific expansion of the underlying gene families, driven by recurrent genome and gene duplications followed by functional divergence, have facilitated the evolution of both conserved and specialized metabolic branches and natural products. Functionally, conserved terpenoids act as phytohormones, signaling molecules, and pigments governing plant growth and development, whereas typically species-specific specialized terpenoids mediate dynamic plant-environment interactions, including pest and pathogen defenses, allelopathy, pollinator attraction, root-microbiome communication, and abiotic stress tolerance. Advances in genomics, metabolomics, and synthetic biology continue to accelerate the discovery of terpenoid structures, pathways, and functions at an ever-increasing pace. Elucidating the mechanisms that generate this diversity, and the multifaceted roles that terpenoids play in plant ecology and physiology not only deepens our understanding of the evolutionary history of terrestrial plants, but also unlocks new opportunities for biotechnological innovation, spanning terpenoid-derived therapeutics, biofuels, fragrances, polymers, agrochemicals, and many other bioproducts.