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Protein-protein interactions (PPIs) mediate many fundamental cellular processes and their control through optically or chemically responsive protein domains has a profound impact on basic research and some clinical applications. Most available chemogenetic methods induce the association, i.e., dimerization or oligomerization, of target proteins, and the few available dissociation approaches either break large oligomeric protein clusters or heteromeric complexes. Here, we have exploited the controlled dissociation of a dimeric oxidoreductase from mycobacteria (MSMEG_2027) by its native cofactor, F420, which is not present in mammals, as a bioorthogonal monomerization switch. We found that in the absence of F420, MSMEG_2027 forms a unique domain-swapped dimer that occludes the cofactor binding site. Substantial remodelling of the intertwined N-terminal helix upon F420binding results in the dissolution of the dimer. We then show that MSMEG_2027 can be expressed as fusion proteins in human cells and apply it as a tool to induce and release MAPK/ERK signalling downstream of a chimeric fibroblast growth factor receptor 1 (FGFR1) tyrosine kinase. This F420-dependent chemogenetic de-dimerization tool is stoichiometric, based on a single domain and presents a novel mechanism to investigate protein complexesin situ.

Over 30 years ago, an intriguing posttranslational modification was found responsible for creating concanavalin A (conA), a carbohydrate-binding protein from jack bean (Canavalia ensiformis) seeds and a common carbohydrate chromatography reagent. ConA biosynthesis involves what was then an unprecedented rearrangement in amino-acid sequence, whereby the N-terminal half of the gene-encoded conA precursor (pro-conA) is swapped to become the C-terminal half of conA. Asparaginyl endopeptidase (AEP) was shown to be involved, but its mechanism was not fully elucidated. To understand the structural basis and consequences of circular permutation, we generated recombinant jack bean pro-conA plus jack bean AEP (CeAEP1) and solved crystal structures for each to 2.1 and 2.7 Å, respectively. By reconstituting conA biosynthesis in vitro, we prove CeAEP1 alone can perform both cleavage and cleavage-coupled transpeptidation to form conA. CeAEP1 structural analysis reveals how it is capable of carrying out both reactions. Biophysical assays illustrated that pro-conA is less stable than conA. This observation was explained by fewer intermolecular interactions between subunits in the pro-conA crystal structure and consistent with a difference in the prevalence for tetramerization in solution. These findings elucidate the consequences of circular permutation in the only posttranslation example known to occur in nature.

We recently reported that the membrane-associated progesterone receptor (MAPR) protein family (mammalian members: PGRMC1, PGRMC2, NEUFC and NENF) originated from a new class of prokaryotic cytochrome b

Scribble (Scrib) is a highly conserved cell polarity regulator that harbours potent tumour suppressor activity and plays an important role in cell migration. Dysregulation of polarity is associated with poor prognosis during viral infections. Human T-cell lymphotrophic virus-1 (HTLV-1) encodes for the oncogenic Tax1 protein, a modulator of the transcription of viral and human proteins that can cause cell cycle dysregulation as well as a loss of genomic integrity. Previous studies established that Scribble interacts with Tax1 via its C-terminal PDZ-binding motif (PBM), leading to aggregation of polarity regulators and subsequent perturbation of host cell adhesion, proliferation, and signalling. Using isothermal titration calorimetry, we now show that all four PDZ domains of Scribble bind to Tax1 PBM. We then determined crystal structures of Scribble PDZ1, PDZ2 and PDZ3 domains bound to Tax1 PBM. Our findings establish a structural basis for Tax1-mediated subversion of Scribble-mediated cell polarity signalling and provide the platform for mechanistic studies to examine Tax1 induced mislocalization of Scribble and the associated changes in cellular architecture and subsequent tumorigenesis.

There are three amino acid biosynthesis pathways that are targeted by current herbicides, namely those leading to the production of aromatic amino acids, branched chain amino acids and glutamine. However, their efficacy is diminishing as a result of the increasing number of resistant weeds. Indeed, resistance to most classes of herbicides is on the rise, posing a significant threat to the utility of current herbicides to sustain effective weed management. This review provides an overview of potential herbicide targets within amino acid biosynthesis that remain unexploited commercially, and recent inhibitor discovery efforts. Despite contemporary approaches to herbicide discovery, such as chemical repurposing and the use of omics technologies, there have been no new products introduced to the market that inhibit amino acid biosynthesis over the past three decades. This highlights the chasm that exists between identifying a potent inhibitor and introducing a commercial herbicide. The unpredictability of a mode of action at the systemic level, as well as poor physicochemical properties, often contribute to a lack of progression beyond the target inhibition stage. Nevertheless, it will be important to overcome these obstacles for the development of new herbicides to protect our agricultural industry and ensure food security for an increasing world population. © 2020 Society of Chemical Industry.

Herbicide resistance represents one of the biggest threats to our natural environment and agricultural sector. Thus, new herbicides are urgently needed to tackle the rise in herbicideresistant weeds. Here, we employed a novel strategy to repurpose a ‘failed’ antibiotic into a new and target-specific herbicidal compound. Specifically, we identified an inhibitor of bacterial dihydrodipicolinate reductase (DHDPR), an enzyme involved in lysine biosynthesis in plants and bacteria, that exhibited no antibacterial activity but severely attenuated germination of the plant Arabidopsis thaliana. We confirmed that the inhibitor targets plant DHDPR orthologues in vitro, and exhibits no toxic effects against human cell lines. A series of analogues were then synthesised with improved efficacy in germination assays and against soil-grown A. thaliana plants. We also showed that our lead compound is the first lysine biosynthesis inhibitor with herbicidal activity against a weed species, providing proof-of-concept that DHDPR inhibition may represent a much-needed new herbicide mode of action. Furthermore, this study exemplifies the untapped potential of repurposing ‘failed’ antibiotic scaffolds to fast-track the development of herbicide candidates targeting the respective plant enzymes to combat the global rise in herbicide-resistant weeds.

The boom in growth of 1,4-disubstituted triazole products, in particular, since the early 2000's, can be largely attributed to the birth of click chemistry and the discovery of the CuI -catalyzed azide-alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1-substituted-1,2,3-triazoles has been surprisingly more challenging. Reported here is a straightforward and scalable click-inspired protocol for the synthesis of 1-substituted-1,2,3-triazoles from organic azides and the bench stable acetylene surrogate ethenesulfonyl fluoride (ESF). The new transformation tolerates a wide selection of substrates and proceeds smoothly under metal-free conditions to give the products in excellent yield. Under controlled acidic conditions, the 1-substituted-1,2,3-triazole products undergo a Michael addition reaction with a second equivalent of ESF to give the unprecedented 1-substituted triazolium sulfonyl fluoride salts.

A post-synthetic modification and metallation procedure has been used to prepare a family of heterobimetallic Au(i)-Ag(i) and Au(i)-Hg(ii) complexes featuring either symmetrical or asymmetrical bis-N-heterocyclic carbene ligands with methylene or ethylene linker groups. This synthetic approach is versatile and allows for the synthesis of heterobimetallic complexes bearing asymmetrical ligands that differ in the nature of the NHC wingtip substituents (dimethyl, diethyl or ethyl-methyl) and for the selective placement of the different metal ions. The synthesised complexes were characterised using 1H and 13C NMR spectroscopy and high resolution mass spectrometry (HR-MS) and in the case of complexes 4a, 5b and 8b by X-ray crystallography. The complexes of the methylene linked bridging ligands display conformational isomerism in solution and the conformations adopted by selected compounds were examined using variable temperature (VT) 1H NMR studies. The antibacterial properties of the heterobimetallic Au(i)-Ag(i) complexes in addition to the corresponding homobimetallic Ag(i)2, Au(i)2 complexes were evaluated against clinically relevant Gram-positive and Gram-negative bacterial strains. The homobimetallic Au(i)2 complex and precursor pro-ligand displayed no antibacterial activity up to 256 μg mL-1, whereas the homobimetallic Ag(i)2 was active against all Gram-positive and Gram-negative bacterial strains tested (MIC = 8-32 μg mL-1). Interestingly, both Au(i)-Ag(i) heterobimetallic complexes displayed similar broad-spectrum activity (MIC = 4-32 μg mL-1) to the Ag(i)2 homobimetallic complex.

The 1,2,3-triazole group is one of the most important connective linkers and functional aromatic heterocycles in modern chemistry. The boom in growth of, in particular, 1,4-disubstituted triazole products since the early 2000’s, can be largely attributed to the birth of click chemistry and the discovery of the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1-substituted-1,2,3-triazoles, has been surprisingly more challenging. We report a straightforward and scalable click-protocol for the synthesis of 1-substituted-1,2,3-triazoles from organic azides and the bench stable acetylene-surrogate, ethenesulfonyl fluoride (ESF). The transformation proceeds through a thermal 1,3-dipolar cycloaddition of the azide and ESF to give a sulfonyl fluoride substituted triazoline, that itself spontaneously aromatizes through formal loss of HF/SO2 to give the stable triazole products with excellent fidelity. The new click reaction tolerates a wide selection of substrates and proceeds smoothly under metal-free conditions to give the products in excellent yield, and without need for additives or chromatographic purification. Further, under controlled conditions, the 1-substituted-1,2,3-triazole products undergo Michael reaction with a second equivalent of ESF to give the unprecedented 1-substituted triazolium sulfonyl fluoride salts, demonstrating the versatility and orthogonal reactivity of ESF. The importance of this novel method is evidenced through the late-stage modification of several drugs and drug fragments, including the synthesis of a new improved derivative of the famous antibiotic, chloramphenicol.