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Proceedings of the National Academy of... Jun 2024Patients with type 1 diabetes mellitus who are dependent on an external supply of insulin develop insulin-derived amyloidosis at the sites of insulin injection. A major...
Patients with type 1 diabetes mellitus who are dependent on an external supply of insulin develop insulin-derived amyloidosis at the sites of insulin injection. A major component of these plaques is identified as full-length insulin consisting of the two chains A and B. While there have been several reports that characterize insulin misfolding and the biophysical properties of the fibrils, atomic-level information on the insulin fibril architecture remains elusive. We present here an atomic resolution structure of a monomorphic insulin amyloid fibril that has been determined using magic angle spinning solid-state NMR spectroscopy. The structure of the insulin monomer yields a U-shaped fold in which the two chains A and B are arranged in parallel to each other and are oriented perpendicular to the fibril axis. Each chain contains two β-strands. We identify two hydrophobic clusters that together with the three preserved disulfide bridges define the amyloid core structure. The surface of the monomeric amyloid unit cell is hydrophobic implicating a potential dimerization and oligomerization interface for the assembly of several protofilaments in the mature fibril. The structure provides a starting point for the development of drugs that bind to the fibril surface and disrupt secondary nucleation as well as for other therapeutic approaches to attenuate insulin aggregation.
Topics: Humans; Amyloid; Insulin; Models, Molecular; Hydrophobic and Hydrophilic Interactions; Diabetes Mellitus, Type 1; Protein Conformation; Magnetic Resonance Spectroscopy
PubMed: 38809711
DOI: 10.1073/pnas.2401458121 -
Nature Communications May 2024Cryptophyte algae are an evolutionarily distinct and ecologically important group of photosynthetic unicellular eukaryotes. Photosystem II (PSII) of cryptophyte algae...
Cryptophyte algae are an evolutionarily distinct and ecologically important group of photosynthetic unicellular eukaryotes. Photosystem II (PSII) of cryptophyte algae associates with alloxanthin chlorophyll a/c-binding proteins (ACPs) to act as the peripheral light-harvesting system, whose supramolecular organization is unknown. Here, we purify the PSII-ACPII supercomplex from a cryptophyte alga Chroomonas placoidea (C. placoidea), and analyze its structure at a resolution of 2.47 Å using cryo-electron microscopy. This structure reveals a dimeric organization of PSII-ACPII containing two PSII core monomers flanked by six symmetrically arranged ACPII subunits. The PSII core is conserved whereas the organization of ACPII subunits exhibits a distinct pattern, different from those observed so far in PSII of other algae and higher plants. Furthermore, we find a Chl a-binding antenna subunit, CCPII-S, which mediates interaction of ACPII with the PSII core. These results provide a structural basis for the assembly of antennas within the supercomplex and possible excitation energy transfer pathways in cryptophyte algal PSII, shedding light on the diversity of supramolecular organization of photosynthetic machinery.
Topics: Photosystem II Protein Complex; Cryptophyta; Cryoelectron Microscopy; Chlorophyll; Chlorophyll Binding Proteins; Protein Multimerization; Chlorophyll A; Models, Molecular; Light-Harvesting Protein Complexes
PubMed: 38806516
DOI: 10.1038/s41467-024-48878-x -
Nature Communications May 2024The multidrug efflux transporter EmrE from Escherichia coli requires anionic residues in the substrate binding pocket for coupling drug transport with the proton motive...
The multidrug efflux transporter EmrE from Escherichia coli requires anionic residues in the substrate binding pocket for coupling drug transport with the proton motive force. Here, we show how protonation of a single membrane embedded glutamate residue (Glu14) within the homodimer of EmrE modulates the structure and dynamics in an allosteric manner using NMR spectroscopy. The structure of EmrE in the Glu14 protonated state displays a partially occluded conformation that is inaccessible for drug binding by the presence of aromatic residues in the binding pocket. Deprotonation of a single Glu14 residue in one monomer induces an equilibrium shift toward the open state by altering its side chain position and that of a nearby tryptophan residue. This structural change promotes an open conformation that facilitates drug binding through a conformational selection mechanism and increases the binding affinity by approximately 2000-fold. The prevalence of proton-coupled exchange in efflux systems suggests a mechanism that may be shared in other antiporters where acid/base chemistry modulates access of drugs to the substrate binding pocket.
Topics: Escherichia coli Proteins; Escherichia coli; Antiporters; Binding Sites; Protein Binding; Protons; Protein Conformation; Magnetic Resonance Spectroscopy; Glutamic Acid; Models, Molecular
PubMed: 38806470
DOI: 10.1038/s41467-024-48803-2 -
Biotech (Basel (Switzerland)) May 2024The enzymatic hydrolysis of agricultural residues like wheat bran enables the valorization of otherwise unused carbon sources for biotechnological processes. The...
The enzymatic hydrolysis of agricultural residues like wheat bran enables the valorization of otherwise unused carbon sources for biotechnological processes. The co-culture of and with wheat bran particles as substrate produces an enzyme set consisting of xylanases, amylases, and cellulases that is suitable to degrade lignocellulosic biomass to sugar monomers (D-glucose, D-xylose, and L-arabinose). An integrated one-pot process for enzyme production followed by hydrolysis in stirred tank bioreactors resulted in hydrolysates with overall sugar concentrations of 32.3 g L and 24.4 g L at a 25 L and a 1000 L scale, respectively, within 86 h. Furthermore, the residual solid biomass consisting of fermented wheat bran with protein-rich fungal mycelium displays improved nutritional properties for usage as animal feed due to its increased content of sugars, protein, and fat.
PubMed: 38804297
DOI: 10.3390/biotech13020015 -
Nature Communications May 2024Recycling strategies for mixed plastics and textile blends currently aim for recycling only one of the components. Here, we demonstrate a water coupling strategy to...
Recycling strategies for mixed plastics and textile blends currently aim for recycling only one of the components. Here, we demonstrate a water coupling strategy to co-hydrolyze polyester/cotton textile blends into polymer monomers and platform chemicals in gamma-valerolactone. The blends display a proclivity for achieving an augmented 5-hydroxymethylfurfural yield relative to the degradation of cotton alone. Controlled experiments and preliminary mechanistic studies underscore that the primary driver behind this heightened conversion rate lies in the internal water circulation. The swelling and dissolving effect of gamma-valerolactone on polyester enables a fast hydrolysis of polyester at much lower concentration of acid than the one in the traditional hydrolysis methods, effectively mitigating the excessive degradation of cotton-derived product and undesirable product formation. In addition, the system is also applicable to different kinds of blends and PET mixed plastics. This strategy develops an attractive path for managing end-of-life textiles in a sustainable and efficient way.
PubMed: 38802467
DOI: 10.1038/s41467-024-48937-3 -
Nature Communications May 2024Actin nucleotide-dependent actin remodeling is essential to orchestrate signal transduction and cell adaptation. Rapid energy starvation requires accurate and timely...
Actin nucleotide-dependent actin remodeling is essential to orchestrate signal transduction and cell adaptation. Rapid energy starvation requires accurate and timely reorganization of the actin network. Despite distinct treadmilling mechanisms of ADP- and ATP-actin filaments, their filament structures are nearly identical. How other actin-binding proteins regulate ADP-actin filament assembly is unclear. Here, we show that Spa2 which is the polarisome scaffold protein specifically remodels ADP-actin upon energy starvation in budding yeast. Spa2 triggers ADP-actin monomer nucleation rapidly through a dimeric core of Spa2 (aa 281-535). Concurrently, the intrinsically disordered region (IDR, aa 1-281) guides Spa2 undergoing phase separation and wetting on the surface of ADP-G-actin-derived F-actin and bundles the filaments. Both ADP-actin-specific nucleation and bundling activities of Spa2 are actin D-loop dependent. The IDR and nucleation core of Spa2 are evolutionarily conserved by coexistence in the fungus kingdom, suggesting a universal adaptation mechanism in the fungal kingdom in response to glucose starvation, regulating ADP-G-actin and ADP-F-actin with high nucleotide homogeneity.
Topics: Actins; Glucose; Saccharomyces cerevisiae Proteins; Saccharomyces cerevisiae; Adenosine Diphosphate; Actin Cytoskeleton; Microfilament Proteins
PubMed: 38802374
DOI: 10.1038/s41467-024-48863-4 -
Materials Today. Bio Jun 2024Oral biofilm is the leading cause of dental caries, which is difficult to completely eradicate because of the complicated biofilm structure. What's more, the hypoxia...
Oral biofilm is the leading cause of dental caries, which is difficult to completely eradicate because of the complicated biofilm structure. What's more, the hypoxia environment of biofilm and low water-solubility of conventional photosensitizers severely restrict the therapeutic effect of photodynamic therapy (PDT) for biofilm. Although conventional photosensitizers could be loaded in nanocarriers, it has reduced PDT effect because of aggregation-caused quenching (ACQ) phenomenon. In this study, we fabricated an oxygen self-sufficient nanodroplet (PFC/TPA@FNDs), which was composed of fluorinated-polymer (FP), perfluorocarbons (PFC) and an aggregation-induced emission (AIE) photosensitizer (Triphenylamine, TPA), to eradicate oral bacterial biofilm and whiten tooth. Fluorinated-polymer was synthesized by polymerizing (Dimethylamino)ethyl methacrylate, fluorinated monomer and 1-nonanol monomer. The nanodroplets could be protonated and behave strong positive charge under bacterial biofilm acid environment promoting nanodroplets deeply penetrating biofilm. More importantly, the nanodroplets had extremely high PFC and oxygen loading efficacy because of the hydrophobic affinity between fluorinated-polymer and PFC to relieve the hypoxia environment and enhance PDT effect. Additionally, compared with conventional ACQ photosensitizers loaded system, PFC/TPA@FNDs could behave superior PDT effect to ablate oral bacterial biofilm under light irradiation due to the unique AIE effect. caries animal model proved the nanodroplets could reduce dental caries area without damaging tooth structure. tooth whitening assay also confirmed the nanodroplets had similar tooth whitening ability compared with commercial tooth whitener HO, while did not disrupt the surface microstructure of tooth. This oxygen self-sufficient nanodroplet provides an alternative visual angle for oral biofilm eradication in biomedicine.
PubMed: 38800565
DOI: 10.1016/j.mtbio.2024.101091 -
RSC Applied Polymers May 2024Biodegradable polyesters with interconnected macroporosity, such as poly(l-lactide) (PLLA) and poly(ε-caprolactone) (PCL), have gained significant importance in the...
Biodegradable polyesters with interconnected macroporosity, such as poly(l-lactide) (PLLA) and poly(ε-caprolactone) (PCL), have gained significant importance in the fields of tissue engineering and separation. This study introduces functional macroinitiators, specifically polycaprolactone triol (PCL) and polyethylene glycol (PEG), both OH-terminated, in the solventless ring-opening polymerization (ROP) of a liquid deep eutectic system monomer (DESm) composed of LLA and CL at a 30 : 70 molar ratio, respectively. The macroinitiators selectively initiate the organocatalyzed ROP of LLA in the DESm during the first polymerization stage, thereby modifying the PLLA architecture. This results in the formation of either branched or linear PLLA copolymers depending on the macroinitiator, PCL and PEG, respectively. In the second stage, the ROP of the CL, which is a counterpart of the DESm, produces PCL that blends with the previously formed PLLA. The insights gained into the PLLA architectures during the first stage of the DESm ROP, along with the overall molecular weight and hydrophobicity of the resulting PLLA/PCL blend in bulk, were advantageously used to design polymerizable high internal phase emulsions (HIPEs) oil-in-DESm. By incorporating a liquid mixture of DESm and macroinitiators (PCL or PEG), stable HIPE formulations were achieved. These emulsions sustained the efficient organocatalyzed ROP of the continuous phase at 37 °C with high conversions. The resulting polymer replicas of the HIPEs, characterized by macroporous and interconnected structures, were subjected to a degradation assay in PBS at pH 7.4 and 37 °C and remained mechanically stable for at least 30 days. Notably, they exhibited the capability to sorb crude oil in a proof-of-concept test, with a rate of 2 g g. The macroporous and interconnected features of the polyHIPEs, combined with their inherent degradation properties, position them as promising degradable polymeric sorbents for efficient separation of hydrophobic fluids from water.
PubMed: 38800513
DOI: 10.1039/d3lp00232b -
ACS Central Science May 2024The programmed synthesis of sequence-defined biomaterials whose monomer backbones diverge from those of canonical α-amino acids represents the next frontier in protein...
The programmed synthesis of sequence-defined biomaterials whose monomer backbones diverge from those of canonical α-amino acids represents the next frontier in protein and biomaterial evolution. Such next-generation molecules provide otherwise nonexistent opportunities to develop improved biologic therapies, bioremediation tools, and biodegradable plastic-like materials. One monomer family of particular interest for biomaterials includes β-hydroxy acids. Many natural products contain isolated β-hydroxy acid monomers, and polymers of β-hydroxy acids (β-esters) are found in polyhydroxyalkanoate (PHA) polyesters under development as bioplastics and drug encapsulation/delivery systems. Here we report that β-hydroxy acids possessing both () and () absolute configuration are substrates for pyrrolysyl-tRNA synthetase (PylRS) enzymes and that ()-β-hydroxy acids are substrates . Using the orthogonal PylRS/tRNA synthetase/tRNA pair, in conjunction with wild-type ribosomes and EF-Tu, we report the cellular synthesis of model proteins containing two ()-β-hydroxy acid residues at internal positions. Metadynamics simulations provide a rationale for the observed preference for the ()-β-hydroxy acid and provide mechanistic insights that inform future engineering efforts. As far as we know, this finding represents the first example of an orthogonal synthetase that acylates tRNA with a β-hydroxy acid substrate and the first example of a protein hetero-oligomer containing multiple expanded-backbone monomers produced .
PubMed: 38799653
DOI: 10.1021/acscentsci.3c01366 -
RSC Advances May 2024The syntheses of high-spin organic polymers have been a daunting task due to the highly reactive nature of organic radicals, especially when they are ferromagnetically...
The syntheses of high-spin organic polymers have been a daunting task due to the highly reactive nature of organic radicals, especially when they are ferromagnetically coupled. In this paper, we report our approach to obtain high-spin organic polymers, in which a reasonably stable fluorenyl radical was employed as the primary radical unit, and -triazine serves as the connector that facilitates ferromagnetic coupling between them. Initially, the diamagnetic polymer precursor was synthesized by cyclotrimerization of a cyano-monomer. Subsequently, the high-spin polymers were obtained by oxidizing corresponding anionic polymers using O (6) or I (7). The temperature-dependent magnetic moments, and field-dependent magnetization data obtained from SQUID measurements revealed ferromagnetic couplings between primary radical units, with coupling = 7.5 cm and 38.6 cm. The percentages of primary unit in the radical form are 29%, and 47% for 6 and 7, respectively. Notably, this marks the first reported instance of a high-spin fluorenyl radical polymer exhibiting ferromagnetic coupling.
PubMed: 38799211
DOI: 10.1039/d4ra03034f