Role of Human Mitochondrial Ketosynthase in Long-Chain Fatty Acid Biosynthesis.

Although ketosynthases in bacterial type II fatty acid biosynthesis have been extensively studied, the human mitochondrial ketosynthase, OXSM, remains incompletely characterized. Contrary to the assumption that the role of mitochondrial fatty acid biosynthesis is limited to the production of the lipoic acid precursor octanoate, recent studies suggest an ability to produce longer chain fatty acids. Here, we employ covalent, dual site-selective cross-linkers to trap the interactions between OXSM and its mitochondrial acyl carrier protein partner, mACP.

Visualizing acyl carrier protein interactions within a crosslinked type I polyketide synthase.

Using a combination of dual covalent crosslinking and cryo-EM analyses, we elucidate the structure of mycocerosic acid synthase from Mycobacterium tuberculosis trapped in two distinct catalytic states during its iterative cycle. These structures reveal domain architecture of the acyl carrier protein mediating condensation and dehydration through dual site-selective crosslinking of the acyl carrier protein with the ketosynthase and dehydratase domains. Map density was sufficient to visualize full domain architecture with active site-bound probes and elucidate key interactions of four distinct crosslinked species.

Structural Characterization of an Endogenous Algal Acyl-ACP Thioesterase.

Fatty acids of specific chain lengths offer precursors for high-value renewable energy and fine chemicals industries. In plants and algae, the fatty acid chain length is determined by thioesterase-mediated hydrolysis of fatty acids from acyl carrier proteins through a hitherto unclear mechanism. Herein, a 2.

Identification and Overexpression of Endogenous Transcription Factors to Enhance Lipid Accumulation in the Commercially Relevant Species .

Sustainable low-carbon energy solutions are critical to mitigating global carbon emissions. Algae-based platforms offer potential by converting carbon dioxide into valuable products while aiding carbon sequestration. However, scaling algae cultivation faces challenges like contamination in outdoor systems.

Optimization of the Gold Nanoparticle Colorimetric Assay for Screening and Quantifying Ice Recrystallization Inhibition Activity of Antifreeze Proteins.

Antifreeze proteins or ice-binding proteins can be found in a variety of organisms, including fish, insects, and plants. These proteins are responsible for hindering ice crystal growth, a process known as ice recrystallization inhibition (IRI), allowing the organism to survive in subzero temperatures. Antifreeze proteins are an attractive area of research because of their potential applications in wide-ranging areas, such as food and crops preservation, industry, and cryopreservation.

Engineering regiospecific methylation of the pladienolides.

Well-recognized for the ability to modulate spliceosome activity, the pladienolide family of polyketide natural products has been the recent subject of intense synthetic and bioactivity studies. However, our understanding of their biosynthesis remains incomplete. Here, we report the biosynthetic gene cluster of FD-895 from A-9561 and explore the installation of a key methylation important for metabolite stability.

Elucidating the Iterative Elongation Mechanism in a Type III Polyketide Synthase.

Type III polyketide synthases (PKSs) have a much simpler three-dimensional architecture compared with their type I and type II counterparts, yet they catalyze iterative polyketide elongation to generate a myriad of products in plants, fungi, and eubacteria. Despite this mechanistic complexity occurring within a single active site, the mechanism by which type III PKSs stabilize and direct their highly reactive keto and enolate intermediates has yet to be fully understood. Here, we report the synthesis and deployment of stable polyketone CoA analogues for each putative intermediate involved in the biphenyl synthase (BIS) mechanism together with three high-resolution crystal structures of each in complex with BIS from .

Renewable Terephthalates and Aromatic Diisocyanates from Galactose.

Aromatic diisocyanates, invaluable commodity chemicals for polymer manufacturing, are produced annually on megaton scales from petroleum-derived diamines via phosgenation. Existing routes toward renewable alternatives are sparse and limited by access to functionalized aromatic starting materials, such as terephthalates. Herein, we report the development of a robust route to renewable terephthalates and aromatic diisocyanates from D-galactose via Eastwood olefination and Diels-Alder cycloaddition, followed by a mild electrochemical decarboxylative aromatization.

Engineering the Novel Extremophile Alga for High Lipid and High Starch Production as a Path to Developing Commercially Relevant Strains.

Microalgae offer a compelling platform for the production of commodity products, due to their superior photosynthetic efficiency, adaptability to nonarable lands and nonpotable water, and their capacity to produce a versatile array of bioproducts, including biofuels and biomaterials. However, the scalability of microalgae as a bioresource has been hindered by challenges such as costly biomass production related to vulnerability to pond crashes during large-scale cultivation. This study presents a pipeline for the genetic engineering and pilot-scale production of biodiesel and thermoplastic polyurethane precursors in the extremophile species .

Manipulation and Structural Activity of AcpM in .

(Mtb) is a leading cause of death, with an escalating global occurrence of drug-resistant infections that are partially attributed to cell wall mycolic acids derived from type II fatty acid biosynthesis (FAS-II). Here, the central acyl carrier protein, AcpM, contributes to the regulation of complex and specific protein-protein interactions (PPIs), though the orchestration of these events remain largely unresolved due to unique features of AcpM. Limitations include complexities in generating modified AcpM in a single state.

Crosslinking intermodular condensation in non-ribosomal peptide biosynthesis.

Non-ribosomal peptide synthetases are assembly line biosynthetic pathways that are used to produce critical therapeutic drugs and are typically arranged as large multi-domain proteins called megasynthetases. They synthesize polypeptides using peptidyl carrier proteins that shuttle each amino acid through modular loading, modification and elongation steps, and remain challenging to structurally characterize, owing in part to the inherent dynamics of their multi-domain and multi-modular architectures. Here we have developed site-selective crosslinking probes to conformationally constrain and resolve the interactions between carrier proteins and their partner enzymatic domains.

Possible Missing Sources of Atmospheric Glyoxal Part II: Oxidation of Toluene Derived from the Primary Production of Marine Microorganisms.

Background: Glyoxal has been implicated as a significant contributor to the formation of secondary organic aerosols, which play a key role in our ability to estimate the impact of aerosols on climate. Elevated concentrations of glyoxal over open ocean waters suggest that there exists an additional source, different from urban and forest environments, which has yet to be identified.

Methods: Based on mass spectrometric analyses of nascent sea spray aerosols (SSAs) and gas-phase molecules generated during the course of a controlled algal bloom, the work herein suggests that marine microorganisms are capable of excreting toluene in response to environmental stimuli.

Differentiating carrier protein interactions in biosynthetic pathways using dapoxyl solvatochromism.

Carrier protein-dependent synthases are ubiquitous enzymes involved both in primary and secondary metabolism. Biocatalysis within these synthases is governed by key interactions between the carrier protein, substrate, and partner enzymes. The weak and transient nature of these interactions has rendered them difficult to study.

A temperature-sensitive metabolic valve and a transcriptional feedback loop drive rapid homeoviscous adaptation in Escherichia coli.

All free-living microorganisms homeostatically maintain the fluidity of their membranes by adapting lipid composition to environmental temperatures. Here, we quantify enzymes and metabolic intermediates of the Escherichia coli fatty acid and phospholipid synthesis pathways, to describe how this organism measures temperature and restores optimal membrane fluidity within a single generation after a temperature shock. A first element of this regulatory system is a temperature-sensitive metabolic valve that allocates flux between the saturated and unsaturated fatty acid synthesis pathways via the branchpoint enzymes FabI and FabB.

Cryptic Cerulenin Rearrangement in Ketosynthase Covalent Inhibition.

The antibiotic cerulenin is a fungal natural product identified as a covalent inhibitor of ketosynthases within fatty acid and polyketide biosynthesis. Due to its selective and potent inhibitory activity, cerulenin has found significant utility in multidisciplinary biochemical, biomedical, and clinical studies. Although its covalent inhibition profile has been confirmed, cerulenin's mechanism has not been fully determined at a molecular level, frustrating the drug development of related analogues.

Fluorometric Analysis of Carrier-Protein-Dependent Biosynthesis through a Conformationally Sensitive Solvatochromic Pantetheinamide Probe.

Carrier proteins (CPs) play a fundamental role in the biosynthesis of fatty acids, polyketides, and non-ribosomal peptides, encompassing many medicinally and pharmacologically relevant compounds. Current approaches to analyze novel carrier-protein-dependent synthetic pathways are hampered by a lack of activity-based assays for natural product biosynthesis. To fill this gap, we turned to 3-methoxychromones, highly solvatochromic fluorescent molecules whose emission intensity and wavelength are heavily dependent on their immediate molecular environment.

Quantitative Characterization of Chain-Flipping of Acyl Carrier Protein of Using Chemical Exchange NMR.

The acyl carrier protein of , termed AcpP, is a prototypical example of type II fatty acid synthase systems found in many bacteria. It serves as a central hub by accepting diverse acyl moieties (4-18 carbons) and shuttling them between its multiple enzymatic partners to generate fatty acids. Prior structures of acyl-AcpPs established that thioester-linked acyl cargos are sequestered within AcpP's hydrophobic lumen.

Rapid biodegradation of microplastics generated from bio-based thermoplastic polyurethane.

The accumulation of microplastics in various ecosystems has now been well documented and recent evidence suggests detrimental effects on various biological processes due to this pollution. Accumulation of microplastics in the natural environment is ultimately due to the chemical nature of widely used petroleum-based plastic polymers, which typically are inaccessible to biological processing. One way to mitigate this crisis is adoption of plastics that biodegrade if released into natural environments.

Visualizing the Interface of Biotin and Fatty Acid Biosynthesis through SuFEx Probes.

Site-specific covalent conjugation offers a powerful tool to identify and understand protein-protein interactions. In this study, we discover that sulfur fluoride exchange (SuFEx) warheads effectively crosslink the acyl carrier protein (AcpP) with its partner BioF, a key pyridoxal 5'-phosphate (PLP)-dependent enzyme in the early steps of biotin biosynthesis by targeting a tyrosine residue proximal to the active site. We identify the site of crosslink by MS/MS analysis of the peptide originating from both partners.

Substrate Sequestration and Chain Flipping in Human Mitochondrial Acyl Carrier Protein.

Outside of their involvement in energy production, mitochondria play a critical role for the cell through their access to a discrete pathway for fatty acid biosynthesis. Despite decades of study in bacterial fatty acid synthases (the putative evolutionary mitochondrial precursor), our understanding of human mitochondrial fatty acid biosynthesis remains incomplete. In particular, the role of the key carrier protein, human mitochondrial acyl carrier protein (mACP), which shuttles the substrate intermediates through the pathway, has not been well-studied in part due to challenges in protein expression and purification.

Masked cerulenin enables a dual-site selective protein crosslink.

Protein-reactive natural products such as the fungal metabolite cerulenin are recognized for their value as therapeutic candidates, due to their ability to selectively react with catalytic residues within a protein active site or a complex of protein domains. Here, we explore the development of fatty-acid and polyketide-synthase probes by synthetically modulating cerulenin's functional moieties. Using a mechanism-based approach, we reveal unique reactivity within cerulenin and adapt it for fluorescent labeling and crosslinking of fatty-acid and iterative type-I polyketide synthases.

Interface Engineering of Carrier-Protein-Dependent Metabolic Pathways.

Carrier-protein-dependent metabolic pathways biosynthesize fatty acids, polyketides, and non-ribosomal peptides, producing metabolites with important pharmaceutical, environmental, and industrial properties. Recent findings demonstrate that these pathways rely on selective communication mechanisms involving protein-protein interactions (PPIs) that guide enzyme reactivity and timing. While rational design of these PPIs could enable pathway design and modification, this goal remains a challenge due to the complex nature of protein interfaces.

Synthase-selected sorting approach identifies a beta-lactone synthase in a nudibranch symbiotic bacterium.

Background: Nudibranchs comprise a group of > 6000 marine soft-bodied mollusk species known to use secondary metabolites (natural products) for chemical defense. The full diversity of these metabolites and whether symbiotic microbes are responsible for their synthesis remains unexplored. Another issue in searching for undiscovered natural products is that computational analysis of genomes of uncultured microbes can result in detection of novel biosynthetic gene clusters; however, their in vivo functionality is not guaranteed which limits further exploration of their pharmaceutical or industrial potential.

Stereochemical Control of Splice Modulation in FD-895 Analogues.

Highly functionalized skeletons of macrolide natural products gain access to rare spatial arrangements of atoms, where changes in stereochemistry can have a profound impact on the structure and function. Spliceosome modulators present a unique consensus motif, with the majority targeting a key interface within the SF3B spliceosome complex. Our recent preparative-scale synthetic campaign of 17-FD-895 provided unique access to stereochemical analogues of this complex macrolide.