Directed evolution predicts cytochrome b G37V target site modification as probable adaptive mechanism towards the QiI fungicide fenpicoxamid in Zymoseptoria tritici.

Acquired resistance is a threat to antifungal efficacy in medicine and agriculture. The diversity of possible resistance mechanisms and highly adaptive traits of pathogens make it difficult to predict evolutionary outcomes of treatments. We used directed evolution as an approach to assess the resistance risk to the new fungicide fenpicoxamid in the wheat pathogenic fungus Zymoseptoria tritici. Fenpicoxamid inhibits complex III of the respiratory chain at the ubiquinone reduction site (Qi site) of the mitochondrially encoded cytochrome b, a different site than the widely used strobilurins which inhibit the same complex at the ubiquinol oxidation site (Qo site). We identified the G37V change within the cytochrome b Qi site as the most likely resistance mechanism to be selected in Z. tritici. This change triggered high fenpicoxamid resistance and halved the enzymatic activity of cytochrome b, despite no significant penalty for in vitro growth. We identified negative cross-resistance between isolates harbouring G37V or G143A, a Qo site change previously selected by strobilurins. Double mutants were less resistant to both QiIs and quinone outside inhibitors compared to single mutants. This work is a proof of concept that experimental evolution can be used to predict adaptation to fungicides and provides new perspectives for the management of QiIs.

Sulfoxaflor - A sulfoximine insecticide: Review and analysis of mode of action, resistance and cross-resistance.

The sulfoximines, as exemplified by sulfoxaflor (Isoclast™active), are a relatively new class of nicotinic acetylcholine receptor (nAChR) competitive modulator (Insecticide Resistance Action Committee [IRAC] Group 4C) insecticides that provide control of a wide range of sap-feeding insect pests. The sulfoximine chemistry and sulfoxaflor exhibits distinct interactions with metabolic enzymes and nAChRs compared to other IRAC Group 4 insecticides such as the neonicotinoids (Group 4A). These distinctions translate to notable differences in the frequency and degree of cross-resistance between sulfoxaflor and other insecticides. Most insect strains exhibiting resistance to a variety of insecticides, including neonicotinoids, exhibited little to no cross-resistance to sulfoxaflor. To date, only two laboratory-based studies involving four strains (Koo et al. 2014, Chen et al. 2017) have observed substantial cross-resistance (>100 fold) to sulfoxaflor in neonicotinoid resistant insects. Where higher levels of cross-resistance to sulfoxaflor are observed the magnitude of that resistance is far less than that of the selecting neonicotinoid. Importantly, there is no correlation between presence of resistance to neonicotinoids (i.e., imidacloprid, acetamiprid) and cross-resistance to sulfoxaflor. This phenomenon is consistent with and can be attributed to the unique and differentiated chemical class represented by sulfoxalfor. Recent studies have demonstrated that high levels of resistance (resistance ratio = 124-366) to sulfoxaflor can be selected for in the laboratory which thus far appear to be associated with enhanced metabolism by specific cytochrome P450s, although other resistance mechanisms have not yet been excluded. One hypothesis is that sulfoxaflor selects for and is susceptible to a subset of P450s with different substrate specificity. A range of chemoinformatic, molecular modeling, metabolism and target-site studies have been published. These studies point to distinctions in the chemistry of sulfoxaflor, and its metabolism by enzymes associated with resistance to other insecticides, as well as its interaction with insect nicotinic acetylcholine receptors, further supporting the subgrouping of sulfoxaflor (Group 4C) separate from that of other Group 4 insecticides. Herein is an expansion of an earlier review (Sparks et al. 2013), providing an update that considers prior and current studies focused on the mode of action of sulfoxaflor, along with an analysis of the presently available resistance / cross-resistance studies, and implications and recommendations regarding resistance management.

A revised model of fungicide translaminar activity.

Translaminar redistribution is valuable for fungicide activity but difficult to measure and predict. The translaminar activity of 38 fungicides active against cucumber powdery mildew was measured experimentally and used to develop a QSAR (Quantitative structure-activity relationship) model of translaminar movement from calculated parameters. Over 300 physiochemical parameters generated from energy-minimized 3D structures were considered and one-parameter, two-parameter, and five-parameter models were developed. The one-parameter lipophilicity model explained 39% of variability in translaminar activity in the full dataset but none of the variability in the small succinate dehydrogenase inhibitor (SDHI) set. Adding a polar surface area parameter to the lipophilicity parameter improved predictability to 52% and explained over 70% of the variability in the SDHI class. The expanded model with five physiochemical parameters explained more than 80% of the variability in overall translaminar redistribution. The three additional parameters were correlated with molecular size and reactivity. The models were validated with a Leave-One-Out method that showed excellent robustness (r2adj = 0.83, q2 = 0.79, p < .0001) for the five-parameter model. Because the models require only calculated parameters from a 3D chemical structure, they could enable the design or selection of compounds likely to be translaminar.

Safety considerations derived from Cry34Ab1/Cry35Ab1 structure and function.

Insecticidal proteins developed for in-plant protection against crop pests undergo extensive safety testing during the product development process. Safety considerations for insecticidal proteins expressed in crops follow recommended, science-based guidelines and specific studies are conducted on a case by case basis. Corn events expressing Bacillus thuringiensis (Bt) Cry34Ab1 and Cry35Ab1 were developed to protect maize from Diabrotica virgifera virgifera (western corn rootworm) feeding damage. The protein crystal structures of Cry34Ab1 and Cry35Ab1 are different from the more common three-domain Cry or Vip3 proteins expressed in insect resistant maize varieties. Cry34Ab1 is a single domain protein that folds into a beta sandwich structure that resembles membrane-active proteins, including several cytolysins, from a variety of natural sources. Cry35Ab1 has two domains, one domain with structural relatedness to sugar binding motifs and a second domain with an extended beta sheet structure that is clearly related to beta pore forming proteins, some of which are insecticidal, e.g. B. sphaericus BinA/BinB. In this review we discuss Cry34Ab1/Cry35Ab1 structure and function in the context of protein safety studies for insect resistant crops.

The pesticidal Cry6Aa toxin from Bacillus thuringiensis is structurally similar to HlyE-family alpha pore-forming toxins.

BACKGROUND: The Cry6 family of proteins from Bacillus thuringiensis represents a group of powerful toxins with great potential for use in the control of coleopteran insects and of nematode parasites of importance to agriculture. These proteins are unrelated to other insecticidal toxins at the level of their primary sequences and the structure and function of these proteins has been poorly studied to date. This has inhibited our understanding of these toxins and their mode of action, along with our ability to manipulate the proteins to alter their activity to our advantage. To increase our understanding of their mode of action and to facilitate further development of these proteins we have determined the structure of Cry6Aa in protoxin and trypsin-activated forms and demonstrated a pore-forming mechanism of action. RESULTS: The two forms of the toxin were resolved to 2.7 Å and 2.0 Å respectively and showed very similar structures. Cry6Aa shows structural homology to a known class of pore-forming toxins including hemolysin E from Escherichia coli and two Bacillus cereus proteins: the hemolytic toxin HblB and the NheA component of the non-hemolytic toxin (pfam05791). Cry6Aa also shows atypical features compared to other members of this family, including internal repeat sequences and small loop regions within major alpha helices. Trypsin processing was found to result in the loss of some internal sequences while the C-terminal region remains disulfide-linked to the main core of the toxin. Based on the structural similarity of Cry6Aa to other toxins, the mechanism of action of the toxin was probed and its ability to form pores in vivo in Caenorhabditis elegans was demonstrated. A non-toxic mutant was also produced, consistent with the proposed pore-forming mode of action. CONCLUSIONS: Cry6 proteins are members of the alpha helical pore-forming toxins - a structural class not previously recognized among the Cry toxins of B. thuringiensis and representing a new paradigm for nematocidal and insecticidal proteins. Elucidation of both the structure and the pore-forming mechanism of action of Cry6Aa now opens the way to more detailed analysis of toxin specificity and the development of new toxin variants with novel activities.

SAR studies directed toward the pyridine moiety of the sap-feeding insecticide sulfoxaflor (Isoclast™ active).

Sap-feeding insect pests constitute a major insect pest complex that includes a range of aphids, whiteflies, planthoppers and other insect species. Sulfoxaflor (Isoclast™ active), a new sulfoximine class insecticide, targets sap-feeding insect pests including those resistant to many other classes of insecticides. A structure activity relationship (SAR) investigation of the sulfoximine insecticides revealed the importance of a 3-pyridyl ring and a methyl substituent on the methylene bridge linking the pyridine and the sulfoximine moiety to achieving strong Myzus persicae activity. A more in depth QSAR investigation of pyridine ring substituents revealed a strong correlation with the calculated logoctanol/water partition coefficient (SlogP). Model development resulted in a highly predictive model for a set of 18 sulfoximines including sulfoxaflor. The model is consistent with and helps explain the highly optimized pyridine substitution pattern for sulfoxaflor.

Using glycosaminoglycan/chemokine interactions for the long-term delivery of 5P12-RANTES in HIV prevention.

5P12-RANTES is a recently developed chemokine analogue that has shown high level protection from SHIV infection in macaques. However, the feasibility of using 5P12-RANTES as a long-term HIV prevention agent has not been explored partially due to the lack of available delivery devices that can easily be modified for long-term release profiles. Glycosaminoglycans (GAGs) have been known for their affinity for various cytokines and chemokines, including native RANTES, or CCL5. In this work, we investigated used of GAGs in generating a chemokine drug delivery device. Initial studies used surface plasmon resonance analysis to characterize and compare the affinities of different GAGs to 5P12-RANTES. These different GAGs were then incorporated into drug delivery polymeric hydrogels to engineer sustained release of the chemokines. In vitro release studies of 5P12-RANTES from the resulting polymers were performed, and we found that 5P12-RANTES release from these polymers can be controlled by the amount and type of GAG incorporated. Polymer disks containing GAGs with stronger affinity to 5P12-RANTES resulted in more sustained and longer term release than did polymer disks containing GAGs with weaker 5P12-RANTES affinity. Similar trends were observed by varying the amount of GAGs incorporated into the delivery system. 5P12-RANTES released from these polymers demonstrated good levels of CCR5 blocking, retaining activity even after 30 days of incubation.

Microparticle delivery of Interleukin-7 to boost T-cell proliferation and survival.

In HIV infections, homoeostasis of T cells is dysregulated such that there is a depletion of CD4(+) T cells and a progressive loss of naïve CD4(+) and CD8(+) T cells. Methodologies that can improve the function of some or all of these cells will likely enhance immune responsiveness in HIV infection. Interleukin-7 (IL-7) is a cytokine that has been shown to be critical in homeostatic expansion of naïve CD8(+) and CD4(+) cells in lymphopenic hosts, as well as regulating effector T cell to memory T-cell transition and memory T-cell homeostasis. In animal studies and clinical trials, repeated injections of IL-7 are used to boost both CD4(+) and CD8(+) cell counts. Daily injections, however, are painful, inconvenient, and provide a frequent route for pathogen entry. We developed a poly (D,L-lactide-co-glycolide; PLGA) microparticle controlled release system to administer IL-7 in which a single injection of microparticles can provide therapeutic delivery of IL-7. IL-7 encapsulated PLGA microparticles were first synthesized using a water/organic/water double emulsion method, release from the particles was then optimized using in vitro release studies and therapeutic effectiveness was finally studied in animal studies. These PLGA microparticles showed effective delivery of IL-7 for 1 week in vitro. These results were translated to in vivo delivery as well, which was followed for 9 days. Controlled release of IL-7 in mice demonstrated biological activity in both CD4(+) and CD8(+) T cells in mice, which was consistent with previously reported results using daily injections.

Interaction of picolinamide fungicide primary metabolites UK-2A and CAS-649 with the cytochrome bc1 complex Qi site: mutation effects and modelling in Saccharomyces cerevisiae.

BACKGROUND: Fenpicoxamid and florylpicoxamid are picolinamide fungicides targeting the Qi site of the cytochrome bc1 complex, via their primary metabolites UK-2A and CAS-649, respectively. We explore binding interactions and resistance mechanisms for picolinamides, antimycin A and ilicicolin H in yeast by testing effects of cytochrome b amino acid changes on fungicide sensitivity and interpreting results using molecular docking. RESULTS: Effects of amino acid changes on sensitivity to UK-2A and CAS-649 were similar, with highest resistance associated with exchanges involving G37 and substitutions N31K and L198F. These changes, as well as K228M, also affected antimycin A, while ilicicolin H was affected by changes at G37 and L198, as well as Q22E. N31 substitution patterns suggest that a lysine at position 31 introduces an electrostatic interaction with neighbouring D229, causing disruption of a key salt-bridge interaction with picolinamides. Changes involving G37 and L198 imply resistance primarily through steric interference. G37 changes also showed differences between CAS-649 and UK-2A or antimycin A with respect to branched versus unbranched amino acids. N31K and substitution of G37 by large amino acids reduced growth rate substantially while L198 substitutions showed little effect on growth. CONCLUSION: Binding of UK-2A and CAS-649 at the Qi site involves similar interactions such that general cross-resistance between fenpicoxamid and florylpicoxamid is anticipated in target pathogens. Some resistance mutations reduced growth rate and could carry a fitness penalty in pathogens. However, certain changes involving G37 and L198 carry little or no growth penalty and may pose the greatest risk for resistance development in the field. © 2022 Society of Chemical Industry.

Investigation of fragmentation pathways of protonated 2-methoxypyrimidine derivatives.

Several representative pyrimidine derivatives were selected to undergo electrospray ionization (ESI) followed by collision-induced dissociation tandem mass spectrometry (CID MS/MS) experiments. Two competitive pathways were found to govern the formation of major fragment ions from protonated species of these molecules. The pathways were largely affected by the 2-O-methyl group but not significantly influenced by the substitution on C-5 site of the pyrimidine ring. These findings were supported by both deuterium labeling CID MS/MS experiments and theoretical calculations. The deuterium labeled pyrimidine ion molecules were generated in-source in ESI from the fully deuterated hydrazinyl pyrimidines, which were readily obtained through hydrogen/deuterium (H/D) exchange when dissolved in deuterium oxide (D2 O).

Florylpicoxamid, a new picolinamide fungicide with broad spectrum activity.

BACKGROUND: Following the introduction of fenpicoxamid, a natural product-based fungicide targeting the Qi site of mitochondrial cytochrome bc1 complex, a second generation fully synthetic picolinamide, florylpicoxamid, was discovered and its biological activity and attributes were characterized. RESULTS: In vitro fungal growth inhibition assays and in planta glasshouse biological activity evaluations showed florylpicoxamid was active against 21 different plant pathogenic fungi within the phyla Ascomycota and Basidiomycota. Among the pathogens evaluated, florylpicoxamid was most potent against Zymoseptoria tritici, the causal organism of wheat leaf blotch, providing 80% growth inhibition in vitro at 0.0046 mg L-1 and 80% disease control in planta at 0.03 mg L-1 when applied as a preventative treatment. Florylpicoxamid was more efficacious than epoxiconazole, fluxapyroxad, and benzovindiflupyr versus a Z. tritici wild-type isolate when applied as curative and preventative treatments, with superior 10-day curative reachback activity. Analytical studies and in planta tests demonstrated that florylpicoxamid partitioned into plants quickly and showed good systemicity and translaminar activity on both monocot and dicot plants. No cross-resistance was observed between florylpicoxamid and strobilurin or azole fungicides. Florylpicoxamid exerts its preventative effect by preventing spore germination on the leaf surface and curative activity by arresting mycelial growth and pycnidia development in leaf tissue. CONCLUSIONS: With strong broad spectrum fungicidal activity, florylpicoxamid delivers an innovative solution for growers to sustain high productivity and quality of many crops, and also provides a new option for developing effective strategies for fungicide resistance management. © 2021 Society of Chemical Industry.

Transmembrane interactions are needed for KAI1/CD82-mediated suppression of cancer invasion and metastasis.

In transmembrane (TM) domains, tetraspanin KAI1/CD82 contains an Asn, a Gln, and a Glu polar residue. A mutation of all three polar residues largely disrupts the migration-, invasion-, and metastasis-suppressive activities of KAI1/CD82. Notably, KAI1/CD82 inhibits the formation of microprotrusions and the release of microvesicles, while the mutation disrupts these inhibitions, revealing the connections of microprotrusion and microvesicle to KAI1/CD82 function. The TM polar residues are needed for proper interactions between KAI1/CD82 and tetraspanins CD9 and CD151, which also regulate cell movement, but not for the association between KAI1/CD82 and alpha3beta1 integrin. However, KAI1/CD82 still efficiently inhibits cell migration when either CD9 or CD151 is absent. Hence, KAI1/CD82 interacts with tetraspanin and integrin by different mechanisms and is unlikely to inhibit cell migration through its associated proteins. Moreover, without significantly affecting the glycosylation, homodimerization, and global folding of KAI1/CD82, the TM interactions maintain the conformational stability of KAI1/CD82, evidenced by the facts that the mutant is more sensitive to denaturation and less associable with tetraspanins and supported by the modeling analysis. Thus, the TM interactions mediated by these polar residues determine a conformation either in or near the tightly packed TM region and this conformation and/or its change are needed for the intrinsic activity of KAI1/CD82. In contrast to immense efforts to block the signaling of cancer progression, the perturbation of TM interactions may open a new avenue to prevent cancer invasion and metastasis.

Synthesis and biological activity of analogs of the antifungal antibiotic UK-2A. III. Impact of modifications to the macrocycle isobutyryl ester position.

BACKGROUND: Fenpicoxamid (Inatreq™ active), a new fungicide under development by Corteva Agriscience™, Agriculture Division of DowDuPont, is an isobutyryl acetal derivative of the antifungal antibiotic UK-2A. SAR studies around the picolinamide ring and benzyl substituents attached at positions 3 and 8, respectively, of the UK-2A bislactone macrocycle have recently been documented. This study focuses on replacement of the isobutyryl ester group in the 7 position. RESULTS: Thirty analogs, predominantly esters and ethers, were prepared and evaluated for inhibition of mitochondrial electron transport and in vitro growth of Zymoseptoria tritici, Leptosphaeria nodorum, Pyricularia oryzae and Ustilago maydis. Aliphatic substituents containing four to six carbon atoms deliver strong intrinsic activity, the pivaloate ester (IC50 1.44 nM) and the n-butyl, 1-Me-propyl, 3,3-diMe-propyl and 2-c-propyl propyl ethers (IC50 values = 1.08, 1.14, 1.15 & 1.32 nM, respectively) being the most active derivatives. QSAR modelling identified solvation energy (Esolv ) and critical packing parameters (vsurf_CP) as highly significant molecular descriptors for explaining relative intrinsic activity of analogs. Activity translation to fungal growth inhibition and disease control testing was significantly influenced by intrinsic activity and physical properties, the cyclopropanecarboxylate ester (log D 3.67, IC50 3.36 nM, Z. tritici EC50 12 µg L-1 ) showing the strongest Z. tritici activity in protectant tests. CONCLUSIONS: Substitution of the isobutyryl ester group of UK-2A generates analogs that retain strong antifungal activity against Z. tritici and other fungi. © 2019 Society of Chemical Industry.

Identification of tripeptides recognized by the PDZ domain of Dishevelled.

The development of inhibitors of Dishevelled (Dvl) PDZ protein-protein interactions attracts attention due to a possible application in drug discovery and development. Using nuclear magnetic resonance (NMR) spectroscopy, we found that a tripeptide VVV binds to the PDZ domain of Dvl, which is a key component involved in Wnt signaling. Using a computational approach calculating the binding free energy of the complexes of the Dvl PDZ domain and each of the tripeptides VXV (X: any amino acid residue except Pro), we found that a tripeptide VWV had the highest binding affinity. Consistent with the computational result, experimental results showed that the binding of the tripeptide VWV to the Dvl PDZ domain was stronger than that of the tripeptide VVV. The binding affinity of the tripeptide VWV was comparable to that of the organic molecule NSC668036, which was the first identified Dvl PDZ inhibitor. The three-dimensional structure of the complex Dvl1 PDZ/VWV was determined to investigate the role of the energetically favorable W(-1) residue in binding. These interactions were also explored by using molecular dynamic simulation and the molecular mechanics Poisson-Boltzmann surface area method. Taken together, these two tripeptides may be used as modulators of Wnt signaling or as a scaffold to optimize an antagonist for targeting Dvl1 PDZ protein-protein interaction.

Synthesis, stability and insecticidal activity of 2-arylstilbenes.

BACKGROUND: A chemical scaffold-hopping approach from known 3-hydroxyl-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors identified (E/Z)-2-arylstilbenes as novel insecticidal hits against two lepidopteran species, Spodoptera exigua and Trichoplusia ni. A structure-activity relationship (SAR) study of the aryl substituents and the E/Z conformations was carried out in an effort to improve insecticidal potency. RESULTS: A series of (E/Z)-2-arylstilbenes was prepared and separated to evaluate their insecticidal potency against lepidopterous species in diet-feeding assays. The results showed that the (Z)-2-arylstilbenes were more active than their corresponding (E)-isomers, and a stereoselective synthesis was utilized to expand the SAR of the (Z)-2-arylstilbenes. (Z)-4'-Fluoro-3'-methyl-2-(2,4-difluorostyryl)-4-fluoro-5-methoxy-1,1'-biphenyl was the most potent analog in this study with strong activity against S. exigua, T. ni, Helicoverpa zea, Plutella xylostella and Pseudoplusia includens. CONCLUSION: The (Z)-2-arylstilbenes were found to have strong insecticidal potency against five lepidopteran species. Ultimately, synthetic efforts could not improve insecticidal potency to commercial levels, and a lack of UV stability led to efforts being discontinued. © 2019 Society of Chemical Industry.

Synthesis and biological activity of analogs of the antifungal antibiotic UK-2A. II. Impact of modifications to the macrocycle benzyl position.

BACKGROUND: UK-2A is an antifungal antibiotic produced by Streptomyces sp. 517-02. Derivatization of its picolinamide OH to form the isobutyryl acetal led to the discovery of fenpicoxamid (InatreqTM active), which is currently under development as a fungicide by Dow AgroSciences LLC. This paper documents efforts to achieve additional efficacy enhancements through semi-synthetic modification of the benzyl substituent of the UK-2A macrocycle. RESULTS: Of 34 analogs prepared, the most active had mitochondrial electron transport IC50 values 1.5- to 3.7-fold higher than UK-2A (IC50 0.86 nM). The cyclohexyl analog (38, IC50 1.23 nM) was the most intrinsically active derivative, and inhibited in vitro growth of Zymoseptoria tritici (EC50 2.8 ppb) and Leptosphaeria nodorum (EC50 6.2 ppb) more strongly than UK-2A (EC50 5.3 and 11.3 ppb for Z. tritici and L. nodorum, respectively). Heterocyclic ring systems and polar linker functionalities resulted in substantial activity loss. Several analogs (20, 22, 23, 24, 36 and 38) translated Z. tritici in vitro growth inhibition activity to in planta disease control more effectively than did UK-2A, with log D being a key factor in this regard. CONCLUSIONS: UK-2A is amenable to further modification at the benzyl position on the macrocycle, which provides opportunities for manipulation of physical properties while retaining strong intrinsic and antifungal activity. © 2019 Society of Chemical Industry.

Synthesis and biological activity of analogs of the antifungal antibiotic UK-2A. I. Impact of picolinamide ring replacement.

BACKGROUND: The antifungal antibiotic UK-2A strongly inhibits mitochondrial electron transport at the Qi site of the cytochrome bc1 complex. Previous reports have described semi-synthetic modifications of UK-2A to explore the structure-activity relationship (SAR), but efforts to replace the picolinic acid moiety have been limited. RESULTS: Nineteen UK-2A analogs were prepared and evaluated for Qi site (cytochrome c reductase) inhibition and antifungal activity. While the majority are weaker Qi site inhibitors than UK-2A (IC50 , 3.8 nM), compounds 2, 5, 13 and 16 are slightly more active (IC50 , 3.3, 2.02, 2.89 and 1.55 nM, respectively). Compared to UK-2A, compounds 13 and 16 also inhibit growth of Zymoseptoria tritici and Leptosphaeria nodorum more strongly, while 2 and 13 provide stronger control of Z. tritici and Puccinia triticina in glasshouse tests. The relative activities of compounds 1-19 are rationalized based on a homology model constructed for the Z. tritici Qi binding site. Physical properties of compounds 1-19 influence translation of intrinsic activity to antifungal growth inhibition and in planta disease control. CONCLUSIONS: The 3-hydroxy-4-methoxy picolinic acid moiety of UK-2A can be replaced by a variety of o-hydroxy-substituted arylcarboxylic acids that retain strong activity against Z. tritici and other agriculturally relevant fungi. © 2018 Society of Chemical Industry.

Therapeutic use of PDZ protein-protein interaction antagonism.

PDZ domains are important interaction modules in many intracellular pathways and abnormal activations of many of those pathways lead to diseases, including several types of cancer. The domains are characterized by the ability to recognize the extreme COOH-terminus of target proteins, such as G protein-coupled receptors and ion channels. Because PDZ protein-protein interaction is a key factor in the function of cellular pathways and signal transmission in those pathways, developing small-molecule inhibitors to compete with PDZ targets is very attractive in dissecting molecular mechanisms and formulating pharmaceutical agents. Moreover, there is a growing interest in developing small-molecule drugs to block signaling within cells. The modulation of PDZ-involved interactions in cells might be an approach to target the G protein-coupled receptors and ion channels, which are among the most important classes of drug targets in the pharmaceutical industry today. Here, we review recent progress in the development of small-molecule PDZ inhibitors, and especially focus on two PDZ domain-containing target proteins, postsynaptic density 95 and dishevelled.

Characterization of the mechanism of action of the fungicide fenpicoxamid and its metabolite UK-2A.

BACKGROUND: Fenpicoxamid is a new fungicide for control of Zymoseptoria tritici, and is a derivative of the natural product UK-2A. Its mode of action and target site interactions have been investigated. RESULTS: UK-2A strongly inhibited cytochrome c reductase, whereas fenpicoxamid was much less active, consistent with UK-2A being the fungicidally active species generated from fenpicoxamid by metabolism. Both compounds caused rapid loss of mitochondrial membrane potential in Z. tritici spores. In Saccharomyces cerevisiae, amino acid substitutions N31K, G37C and L198F at the Qi quinone binding site of cytochrome b reduced sensitivity to fenpicoxamid, UK-2A and antimycin A. Activity of fenpicoxamid was not reduced by the G143A exchange responsible for strobilurin resistance. A docking pose for UK-2A at the Qi site overlaid that of antimycin A. Activity towards Botrytis cinerea was potentiated by salicylhydroxamic acid, showing an ability of alternative respiration to mitigate activity. Fungitoxicity assays against Z. tritici field isolates showed no cross-resistance to strobilurin, azole or benzimidazole fungicides. CONCLUSION: Fenpicoxamid is a Qi inhibitor fungicide that provides a new mode of action for Z. tritici control. Mutational and modeling studies suggest that the active species UK-2A binds at the Qi site in a similar, but not identical, fashion to antimycin A. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Physicochemical property guidelines for modern agrochemicals.

The relentless need for the discovery and development of new agrochemicals continues as a result of driving forces such as loss of existing products through the development of resistance, the necessity for products with more favorable environmental and toxicological profiles, shifting pest spectra, and the changing agricultural needs and practices of the farming community. These new challenges underscore the demand for novel, high-quality starting points to accelerate the discovery of new agrochemicals that address market challenges. This article discusses the efforts to identify the optimum ranges of physicochemical properties of agrochemicals through analysis of modern commercial products. Specifically, we reviewed literature studies examining physicochemical property effects and analyzed the properties typical of successful fungicides, herbicides, and insecticides (chewing and sap-feeding pests). From the analysis, a new set of physicochemical property guidelines for each discipline, as well as building block class, are proposed. These new guidelines should significantly aid in the discovery of next-generation agrochemicals. © 2018 Society of Chemical Industry.