Cellulose-based materials are produced industrially in countless varieties via top-down processing of natural lignocellulose substrates. By contrast, cellulosic materials are only rarely prepared via ...bottom up synthesis and oligomerization-induced self-assembly of cellulose chains. Building up a cellulose chain via precision polymerization is promising, however, for it offers tunability and control of the final chemical structure. Synthetic cellulose derivatives with programmable material properties might thus be obtained. Cellodextrin phosphorylase (CdP; EC 2.4.1.49) catalyzes iterative β-1,4-glycosylation from α-d-glucose 1-phosphate, with the ability to elongate a diversity of acceptor substrates, including cellobiose, d-glucose and a range of synthetic glycosides having non-sugar aglycons. Depending on the reaction conditions leading to different degrees of polymerization (DP), short-chain soluble cello-oligosaccharides (COS) or insoluble cellulosic materials are formed. Here, we review the characteristics of CdP as bio-catalyst for synthetic applications and show advances in the enzymatic production of COS and reducing end-modified, tailored cellulose materials. Recent studies reveal COS as interesting dietary fibers that could provide a selective prebiotic effect. The bottom-up synthesized celluloses involve chains of DP ≥ 9, as precipitated in solution, and they form ~5 nm thick sheet-like crystalline structures of cellulose allomorph II. Solvent conditions and aglycon structures can direct the cellulose chain self-assembly towards a range of material architectures, including hierarchically organized networks of nanoribbons, or nanorods as well as distorted nanosheets. Composite materials are also formed. The resulting materials can be useful as property-tunable hydrogels and feature site-specific introduction of functional and chemically reactive groups. Therefore, COS and cellulose obtained via bottom-up synthesis can expand cellulose applications towards product classes that are difficult to access via top-down processing of natural materials.
•Cellodextrin phosphorylases (EC 2.4.1.49) as biocatalyst for cello-oligomer synthesis•Structure, specificity and catalytic properties of cellodextrin phosphorylase•Synthesis of reducing end-modified cellulose oligomers for property-tunable materials•Synthesis of soluble cello-oligosaccharides by cascades of glycoside phosphorylases•Applied potential of products synthesized by cellodextrin phosphorylase
Brought to life more than half a century ago and successfully applied for high-value petrochemical intermediates production, nickel-catalyzed olefin oligomerization is still a very dynamic topic, ...with many fundamental questions to address and industrial challenges to overcome. The unique and versatile reactivity of nickel enables the oligomerization of ethylene, propylene, and butenes into a wide range of oligomers that are highly sought-after in numerous fields to be controlled. Interestingly, both homogeneous and heterogeneous nickel catalysts have been scrutinized and employed to do this. This rare specificity encouraged us to interlink them in this review so as to open up opportunities for further catalyst development and innovation. An in-depth understanding of the reaction mechanisms in play is essential to being able to fine-tune the selectivity and achieve efficiency in the rational design of novel catalytic systems. This review thus provides a complete overview of the subject, compiling the main fundamental/industrial milestones and remaining challenges facing homogeneous/heterogeneous approaches as well as emerging catalytic concepts, with a focus on the last 10 years.
γ-conglutin (γ-C) is a hexameric glycoprotein accumulated in lupin seeds and has long been considered as a storage protein. Recently, it has been investigated for its possible postprandial glycaemic ...regulating action in human nutrition and for its physiological role in plant defence. The quaternary structure of γ-C results from the assembly of six monomers in reversible pH-dependent association/dissociation equilibrium. Our working hypothesis was that the γ-C hexamer is made up of glycosylated subunits in association with not-glycosylated isoforms, that seem to have ‘escaped’ the correct glycosylation process in the Golgi. Here we describe the isolation of not-glycosylated γ-C monomers in native condition by two in tandem lectin-based affinity chromatography and the characterization of their oligomerization capacity. We report, for the first time, the observation that a plant multimeric protein may be formed by identical polypeptide chains that have undergone different post-translational modifications. All obtained considered, the results strongly suggest that the not-glycosylated isoform can also take part in the oligomerization equilibrium of the protein.
•A not-glycosylated γ-C monomers from the native protein has been isolated for the first time.•Native γ-C is a hexamer made up by both glycosylated and not-glycosylated monomers.•The seed glycoprotein is formed by identical polypeptide chains that have undergone different PTMs.•The not-glycosylated polypeptide is able to take part in the oligomerization equilibrium of γ-C.
The insightful mechanism of two oligomerization methods using either horseradish peroxide (HRP)/hydrogen peroxide (H2O2) (enzymatic approach), or H2O2 (35% aqueous) (chemical approach) on 4-phenoxy ...aniline (PA) and 4-(4-chlorophenoxy)aniline (PACl) as two amino-functional monomers was studied. Four oligomers synthesized were described by FT-IR, UV-Vis, 1H-NMR and 13C-NMR techniques for the molecular structure analysis. The oligomers substituted with chlorine had stronger electron acceptor ability, which enhanced the intramolecular charge transfer between the donating moiety and chlorine acceptor substituent, resulting in a 48 nm red shift of the λmax for the n→π* electronic transition. Oligomers prepared by horseradish peroxidase shows better fluorescence properties than the monomers. The use of oxidoreductase enzyme (HRP) as the catalyst, for the one-step oligomerization of the monomers demonstrated to yield fluorescent products. Photoluminescence (PL) measurements enlightened that emission quantum yields of PACl-E in DMF were found to be 18% and 4.2% at the maximum emission wavelength of 412 nm and 482 nm, respectively. it is considered as green oligomerization/polymerization method Since HRP catalysis provided a green oxidative oligomerization method of aniline and their derivatives, four oligomers were produced by peroxidase-catalyzed oxidation oligomerization in relation to their electronic properties. HOMO-LUMO energy levels were calculated to make comments about electrochemical (E′g) band gaps of the oligomers which were lower than those of their regarding monomers. SEM images were provided to study the morphology of the oligomers. Intermolecular dihydrophenazine formation in the course of enzymatic oligomerization would eventuate in highly ordered structures.
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•The oligomers of 4-phenoxy aniline and 4-(4-chlorophenoxy)aniline were synthesized via the enzymatic and the chemical oxidative oligomerization routes.•Fluorescence quantum yields of blue emission for the enzymatically synthesized oligomers were calculated as 23% and 18% in DMF solution.•Residual amounts of oligomers synthesized were found to be in the range of 9–16%.•The enzymatic oligomerization could lead to the formation of more regular microstructures owing to the intermolecular dihydrophenazine.
Protein interactions are the foundation of cell biology. For robust signal transduction to occur, proteins interact selectively and modulate their behavior to direct specific biological outcomes. ...Frequently, modular protein interaction domains are central to these processes. Some of these domains bind proteins bearing post‐translational modifications, such as phosphorylation, whereas other domains recognize and bind to specific amino acid motifs. Other modules act as diverse protein interaction scaffolds or can be multifunctional, forming head‐to‐head homodimers and binding specific peptide sequences or membrane phospholipids. Additionally, the so‐called head‐to‐tail oligomerization domains (SAM, DIX, and PB1) can form extended polymers to regulate diverse aspects of biology. Although the mechanism and structures of these domains are diverse, they are united by their modularity. Together, these domains are versatile and facilitate the evolution of complex protein interaction networks. In this review, we will highlight the role of select modular protein interaction domains in various aspects of plant biology.
The ability for proteins to interact is central to their biological functions. Modular protein domains act as a biological toolkit that allow evolution of protein interactions. In this review, we provide a snapshot of how individual domains drive protein versatility and lay the groundwork for complex protein interactions in plants.
Degradation of endoplasmic reticulum (ER) by selective autophagy (ER‐phagy) is crucial for ER homeostasis. However, it remains unclear how ER scission is regulated for subsequent autophagosomal ...sequestration and lysosomal degradation. Here, we show that oligomerization of ER‐phagy receptor FAM134B (also referred to as reticulophagy regulator 1 or RETREG1) through its reticulon‐homology domain is required for membrane fragmentation in vitro and ER‐phagy in vivo. Under ER‐stress conditions, activated CAMK2B phosphorylates the reticulon‐homology domain of FAM134B, which enhances FAM134B oligomerization and activity in membrane fragmentation to accommodate high demand for ER‐phagy. Unexpectedly, FAM134B G216R, a variant derived from a type II hereditary sensory and autonomic neuropathy (HSAN) patient, exhibits gain‐of‐function defects, such as hyperactive self‐association and membrane scission, which results in excessive ER‐phagy and sensory neuron death. Therefore, this study reveals a mechanism of ER membrane fragmentation in ER‐phagy, along with a signaling pathway in regulating ER turnover, and suggests a potential implication of excessive selective autophagy in human diseases.
Synopsis
How endoplasmic reticulum (ER) membranes are fragmented for subsequent autophagic degradation (ER‐phagy) is ill‐defined. CAMK2B‐dependent phosphorylation of ER‐phagy receptor FAM134B promotes its oligomerization and membrane scission activity, a process deregulated in sensory neuropathy.
ER‐phagy receptor FAM134B oligomerizes through its reticulon‐homology domain (RHD).
FAM134B oligomerization is required for ER membrane scission prior to autophagosomal engulfment.
ER stress triggers the activation of CAMK2B, which phosphorylates FAM134B to enhance ER membrane fragmentation and ER‐phagy.
An HSAN type‐II patient‐derived variant, FAM134B‐G216R, forms higher‐order oligomers and induces massive ER‐phagy, which leads to sensory neuron death.
CAMK2B‐dependent phosphorylation of autophagy receptor FAM134B promotes its oligomerization and membrane‐scission activity, a process deregulated in sensory neuropathy.
Designed protein receptors hold diagnostic and therapeutic promise. We now report the design of five consensus leucine‐rich repeat proteins (CLRR4–8) based on the LRR domain of nucleotide‐binding ...oligomerization domain (NOD)‐like receptors involved in the innate immune system. The CLRRs bind muramyl dipeptide (MDP), a bacterial cell wall component, with micromolar affinity. The overall Kd app values ranged from 1.0 to 57 μM as measured by fluorescence quenching experiments. Biphasic fluorescence quenching curves were observed in all CLRRs, with higher affinity Kd1 values ranging from 0.04 to 4.5 μM, and lower affinity Kd2 values ranging from 3.1 to 227 μM. These biphasic binding curves, along with the docking studies of MDP binding to CLRR4, suggest that at least two MDPs bind to each protein. Previously, only single MDP binding was reported. This high‐capacity binding of MDP promises small, soluble, stable CLRR scaffolds as candidates for the future design of pathogen biosensors.
Members of the Pht1 family of plant phosphate (Pi) transporters play vital roles in Pi acquisition from soil and in plantaPi translocation to maintain optimal growth and development. The study of the ...specificities and biochemical properties of Pht1 transporters will contribute to improving the current understanding of plant phosphorus homeostasis and use-efficiency. In this study, we show through split in vivo interaction methods and in vitro analysis of microsomal root tissues that Arabidopsis thalianaPht1;1 and Pht1;4 form homomeric and heteromeric complexes. Transient and heterologous expression of the Pht1;1 variants, Pht1;1Y312D, Pht1;1Y312A and Pht1;1Y312F, was used to analyse the role of a putative Pi binding residue (Tyr 312) in Pht1;1 transporter oligomerization and function. The homomeric interaction among Pht1;1 proteins was disrupted by mutation of Tyr 312 to Asp, but not to Ala or Phe. In addition, the Pht1;1Y312D variant conferred enhanced Pi transport when expressed in yeast cells. In contrast, mutation of Tyr 312 to Ala or Phe did not affect Pht1;1 transport kinetics. Our study demonstrates that modifications to the Pht1;1 higher-order structure affects Pi transport, suggesting that oligomerization may serve as a regulatory mechanism for modulating Pi uptake. Oligomerization has been shown to be an important aspect of regulation and function for some membrane transporters. Herein we demonstrate that the Arabidopsis Pht1;1 and Pht1;4 phosphate transporters form homomeric and heteromeric oligomers. Mutation of a tyrosine residue abolished homo-oligomerization of Pht1;1 and also conferred enhanced phosphate transport when expressed in yeast. The results suggest an active site-oligomerization relationship in which oligomerization serves as a mechanism to regulate transporter activity.
Herein a quenched-flow kinetic technique was applied to calculate the rate constants of 1-hexene and 1-octene oligomerization catalyzed by the Cp2ZrCl2 and Cp2HfCl2/MAO catalyst systems, and ...subsequently a mechanism for the higher α-olefin oligomerization reaction was proposed. The oligomerization results showed that Zr-based catalyst in the oligomerization of 1-octene had the highest activity of 17 in comparison to Hfbased one with an activity value of 15 g oligomer/(mmolCat.h)). According to the obtained results, increasing monomer length led to a shift in molecular weight and polydispersity index value (Mw/Mn) to lower values. Furthermore, the microstructure-viscosity relationship was followed by the calculation of branching ratio and short-chain branching percentage. The obtained results revealed that, the oligomers synthesized by the Cp2HfCl2 catalyst had lower short chain branching ratio value and short-chain branching percentages. According to the kinetic results, the initiation rate constant (ki) of Zr-based catalyst was higher than that of Hf-based catalyst, and the order of calculated propagation rate constants was Zr>Hf for both the 1-hexene and 1-octene-based oligomerizations.
The functionalized covalent organic framework materials play an important role in catalytic application. A convenient tactic is developed to design and synthesize an imine‐linked covalent organic ...frameworks (COFs) material (COF‐PD) with abundant nitrogen atoms, which can provide coordination active site and facilitate the incorporation of COFs with nickel ions. Nickel‐coordinated COF‐PD complex (COF‐PD‐Ni) is prepared and used in ethylene oligomerization. COF‐PD‐Ni displays the highest catalytic activity of 1.98 × 105 g/(mol·Ni·h) in ethylene oligomerization with MAO as co‐catalyst and cyclohexane as solvent. Various reaction parameters including reaction temperature, time, solvent, and the amount of cocatalyst are evaluated in detail, dramatically impacting the catalytic activities as well as the distribution of the products. What is more, the effect of COFs structure on the catalytic performance is also studied, suggesting more coordination sites were more important for high activity.
An imine‐linked covalent organic frameworks (COFs) material (COF‐PD) with abundant nitrogen atoms and large surface area was synthesized to provide coordination active site and facilitate the incorporation of COFs with nickel ions to form nickel‐coordinated COF‐PD complex (COF‐PD‐Ni). The large surface area of COF‐PD‐Ni was far lower than that of COF‐PD before loading nickel because of pore blockage caused by the coordination of Ni2+. COF‐PD‐Ni displayed excellent catalytic activity with a strong preference for the 1‐butene in ethylene oligomerization, which attributed to the faster rate of chain transferring process than the chain propagation because of the confinement effect aroused by pore features of covalent organic frameworks.
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