Cyclotides are plant-derived disulfide-rich cyclic peptides that have a natural function in plant defense and potential for use as agricultural pesticides. Because of their highly constrained topology, they are highly resistant to thermal, chemical, or enzymatic degradation. However, the stability of cyclotides at alkaline pH for incubation times of longer than a few days is poorly studied but important since these conditions could be encountered in the environment, during storage or field application as insecticides. In this study, kalata B1 (kB1), the prototypical cyclotide, was engineered to improve its long-term stability and retain its insecticidal activity via point mutations. We found that substituting either Asn29 or Gly1 to lysine or leucine increased the stability of kB1 by twofold when incubated in an alkaline buffer (pH = 9.0) for 7 days, while retaining its insecticidal activity. In addition, when Gly1 was replaced with lysine or leucine, the mutants could be cyclized using an asparaginyl endopeptidase, in vitro with a yield of â¼90% within 5 min. These results demonstrate the potential to manufacture kB1 mutants with increased stability and insecticidal activity recombinantly or in planta. Overall, the discovery of mutants of kB1 that have enhanced stability could be useful in leading to longer term activity in the field as bioinsecticides.
Cyclotides , Insecticides , Oldenlandia , Cyclotides/genetics , Cyclotides/pharmacology , Cyclotides/chemistry , Insecticides/chemistry , Insecticides/pharmacology , Leucine , Lysine/genetics , Mutagenesis , Plant Proteins/metabolism , Oldenlandia/chemistry , Protein Stability , Animals , Cell Line , Cell Survival/drug effects
The development of novel and safe insecticides remains an important need for a growing world population to protect crops and animal and human health. New chemotypes modulating the insect nicotinic acetylcholine receptors have been recently brought to the agricultural market, yet with limited understanding of their molecular interactions at their target receptor. Herein, we disclose the first crystal structures of these insecticides, namely, sulfoxaflor, flupyradifurone, triflumezopyrim, flupyrimin, and the experimental compound, dicloromezotiaz, in a double-mutated acetylcholine-binding protein which mimics the insect-ion-channel orthosteric site. Enabled by these findings, we discovered novel pharmacophores with a related mode of action, and we describe herein their design, synthesis, and biological evaluation.
Drug Design , Insect Proteins/metabolism , Insecticides/chemical synthesis , Receptors, Nicotinic/metabolism , 4-Butyrolactone/analogs & derivatives , 4-Butyrolactone/chemistry , 4-Butyrolactone/metabolism , Animals , Binding Sites , Coleoptera/drug effects , Coleoptera/metabolism , Crystallography, X-Ray , Humans , Insect Control/methods , Insect Proteins/chemistry , Insect Proteins/genetics , Insecticides/metabolism , Insecticides/pharmacology , Molecular Conformation , Molecular Dynamics Simulation , Mutagenesis, Site-Directed , Pyridines/chemistry , Pyridines/metabolism , Pyrimidinones/chemistry , Pyrimidinones/metabolism , Receptors, Nicotinic/chemistry , Receptors, Nicotinic/genetics , Sulfur Compounds/chemistry , Sulfur Compounds/metabolism
Today, the production of food accounts for roughly one quarter of anthropogenic greenhouse gas emissions. Since the 1970s, thanks to substantial research and development, the overall yield output in farm fields has increased by ca. 60%, while the net use of crop protection agents per square meter of farm field has been reduced by more than 90%. The development of modern crop protection agents remains an important need as new pests, diseases and weeds continue to affect crops. The vast majority of these effective solutions are manufactured using raw materials that ultimately come from fossil resources. In this article, we are touring within the agrochemical landscape to provide the reader with an overview of concrete examples on how in this industrial field, renewable and sustainable raw materials have been used to produce active ingredients. We are also discussing the opportunities for future development as well as some of the challenges and needs that are emerging.
Crop Protection , Crops, Agricultural , Agriculture , Agrochemicals
The insecticidal effects of ω-hexatoxin-Hv1a, κ-hexatoxin-Hv1c and ω/κ-hexatoxin-Hv1h are currently attributed to action at calcium and potassium channels. By characterizing the binding of these toxins to neuronal membranes, we show that they have more potent effects as positive allosteric modulators (PAMs) of insect nicotinic acetylcholine receptors (nAChRs), consistent with their neuroexcitatory toxicology. Alanine scanning analysis of ω-hexatoxin-Hv1a reveals a structure-activity relationship for binding that mirrors that for insecticidal activity. Spinosyn A does not compete with ω-hexatoxin-Hv-1a for binding, and we show that these two PAMs have distinct pharmacology of binding indicating that they act at different receptor populations. These toxins represent valuable tools for the characterization of insect nAChRs and for the development of more selective agrochemicals.
Insecticides/toxicity , Receptors, Nicotinic/drug effects , Spider Venoms/toxicity , Allosteric Regulation , Animals , Humans , Insecticides/chemistry , Spider Venoms/chemistry , Structure-Activity Relationship
The nicotinic acetylcholine receptor (nAChR) is a ligand-gated ion channel composed of 5 protein subunits arranged around a central cation selective pore. Several classes of natural and synthetic insecticides mediate their effect through interacting at nAChRs. This review examines the basic pharmacology of the neonicotinoids and related chemistry, with an emphasis on sap-feeding insects from the order Hemiptera, the principle pest target for such insecticides. Although the receptor subunit stoichiometry for endogenous invertebrate nAChRs is unknown, there is clear evidence for the existence of distinct neonicotinoid binding sites in native insect preparations, which reflects the predicted wide repertoire of nAChRs and differing pharmacology within this insecticide class. The spinosyns are principally used to control chewing pests such as Lepidoptera, whilst nereistoxin analogues are used on pests of rice and vegetables through contact and systemic action, the pharmacology of both these insecticides is unique and different to that of the neonicotinoids.
The structures of the O-glycosyltransferase LanGT2 and the engineered, C-C bond-forming variant LanGT2S8Ac show how the replacement of a single loop can change the functionality of the enzyme. Crystal structures of the enzymes in complex with a nonhydrolyzable nucleotide-sugar analogue revealed that there is a conformational transition to create the binding sites for the aglycon substrate. This induced-fit transition was explored by molecular docking experiments with various aglycon substrates.
Glycosyltransferases/metabolism , Crystallography, X-Ray , Glycosylation , Glycosyltransferases/chemistry , Molecular Docking Simulation , Protein Conformation , Protein Engineering
A new strategy for the catalytic enantioselective α-arylation of N-acyloxazolidinones with chiral copper(II)-bisoxazoline complexes and diaryliodonium salts is described. The mild catalytic conditions are operationally simple, produce valuable synthetic building blocks in excellent yields and enantioselectivities, and can be applied to the synthesis of important nonsteroidal anti-inflammatory agents and their analogues.
Biphenyl Compounds/chemistry , Copper/chemistry , Hydrocarbons, Aromatic/chemistry , Onium Compounds/chemistry , Oxazolidinones/chemistry , Salts/chemistry , Catalysis , Stereoisomerism
The design of a new potent nonsteroidal ecdysone agonist led to the discovery of a diethylaminosulfur trifluoride (DAST)-mediated cyclization of α,α-disubstituted-α-acylaminoketones. The resulting fluorooxazolines can be ring-opened or selectively substituted by a range of nucleophiles to provide in high yields a diverse array of unprecedented heterocyclic frameworks.
Diethylamines/chemistry , Fluorine/chemistry , Heterocyclic Compounds, 1-Ring/chemical synthesis , Ketones/chemistry , Oxazoles/chemical synthesis , Catalysis , Combinatorial Chemistry Techniques , Cyclization , Heterocyclic Compounds, 1-Ring/chemistry , Molecular Structure , Oxazoles/chemistry , Stereoisomerism
A practical one-pot process involving a desymmetrizing hydroformylation with the aid of a chiral catalyst-directing group (CDG*), followed by a carbonyl ene cyclization provides a straightforward access to both enantiomers of the resulting cyclohexanediol; further divergent, highly selective and protecting group-free transformations furnish the carbocyclic analogues of four important 2,6-dideoxysugars.
Carbasugars/chemical synthesis , Ketones/chemistry , Cyclization , Stereoisomerism
Rapid access to highly functionalized alkylidene cyclohexanols through a one-pot desymmetrizing hydroformylation/carbonyl ene cyclization starting from simple bisalkenylcarbinols is reported. Mechanistic insight into the carbonyl ene reaction is given, highlighting the importance of hyperconjugative substituent effects.
Alkenes/chemistry , Cyclohexanols/chemistry , Cyclization , Esters/chemistry , Ferrous Compounds/chemistry , Kinetics , Metallocenes , Methanol/chemistry
