scholarly journals HDQ, a Potent Inhibitor of Plasmodium falciparum Proliferation, Binds to the Quinone Reduction Site of the Cytochromebc1Complex

2012 ◽  
Vol 56 (7) ◽  
pp. 3739-3747 ◽  
Author(s):  
Cindy Vallières ◽  
Nicholas Fisher ◽  
Thomas Antoine ◽  
Mohammed Al-Helal ◽  
Paul Stocks ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Potent Inhibitor ◽  
Single Point ◽  
Point Mutations ◽  
Cross Resistance ◽  
Resistance Mutations ◽  
Inner Mitochondrial Membrane ◽  
Content Type ◽  
Quinone Reduction ◽  
Inhibitor Resistance

ABSTRACTThe mitochondrialbc1complex is a multisubunit enzyme that catalyzes the transfer of electrons from ubiquinol to cytochromeccoupled to the vectorial translocation of protons across the inner mitochondrial membrane. The complex contains two distinct quinone-binding sites, the quinol oxidation site of thebc1complex (Qo) and the quinone reduction site (Qi), located on opposite sides of the membrane within cytochromeb. Inhibitors of the Qosite such as atovaquone, active against thebc1complex ofPlasmodium falciparum, have been developed and formulated as antimalarial drugs. Unfortunately, single point mutations in the Qosite can rapidly render atovaquone ineffective. The development of drugs that could circumvent cross-resistance with atovaquone is needed. Here, we report on the mode of action of a potent inhibitor ofP. falciparumproliferation, 1-hydroxy-2-dodecyl-4(1H)quinolone (HDQ). We show that the parasitebc1complex—from both control and atovaquone-resistant strains—is inhibited by submicromolar concentrations of HDQ, indicating that the two drugs have different targets within the complex. The binding site of HDQ was then determined by using a yeast model. Introduction of point mutations into the Qisite, namely, G33A, H204Y, M221Q, and K228M, markedly decreased HDQ inhibition. In contrast, known inhibitor resistance mutations at the Qosite did not cause HDQ resistance. This study, using HDQ as a proof-of-principle inhibitor, indicates that the Qisite of thebc1complex is a viable target for antimalarial drug development.

scholarly journals Long-Term Dissemination of CTX-M-5-Producing Hypermutable Salmonella enterica Serovar Typhimurium Sequence Type 328 Strains in Russia, Belarus, and Kazakhstan

2014 ◽  
Vol 58 (9) ◽  
pp. 5202-5210 ◽  
Author(s):  
Varvara K. Kozyreva ◽  
Elena N. Ilina ◽  
Maja V. Malakhova ◽  
Alessandra Carattoli ◽  
Ilya S. Azizov ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Genetic Relatedness ◽  
Single Point ◽  
Point Mutations ◽  
Sequence Type ◽  
Quinolone Resistance ◽  
Resistance Mutations ◽  
Content Type ◽  
Serovar Typhimurium

ABSTRACTIn this paper, we present evidence of long-term circulation of cefotaxime-resistant clonally relatedSalmonella entericaserovar Typhimurium strains over a broad geographic area. The genetic relatedness of 88 isolates collected from multiple outbreaks and sporadic cases of nosocomial salmonellosis in various parts of Russia, Belarus, and Kazakhstan from 1996 to 2009 was established by multilocus tandem-repeat analysis (MLVA) and multilocus sequence typing (MLST). The isolates belong to sequence type 328 (ST328) and produce CTX-M-5 β-lactamase, whose gene is carried by highly related non-self-conjugative but mobilizable plasmids. Resistance to nalidixic acid and low-level resistance to ciprofloxacin is present in 37 (42%) of the isolates and in all cases is determined by various single point mutations in thegyrAgene quinolone resistance-determining region (QRDR). Isolates of the described clonal group exhibit a hypermutable phenotype that probably facilitates independent acquisition of quinolone resistance mutations.

scholarly journals Emergence and Spread of kelch13 Mutations Associated with Artemisinin Resistance in Plasmodium falciparum Parasites in 12 Thai Provinces from 2007 to 2016

2018 ◽  
Vol 62 (4) ◽  
Author(s):  
Theerayot Kobasa ◽  
Eldin Talundzic ◽  
Rungniran Sug-aram ◽  
Patcharida Boondat ◽  
Ira F. Goldman ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Gene Mutations ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Resistance Mutations ◽  
Content Type ◽  
Artemisinin Derivatives ◽  
Reduced Ring ◽  
Control And Prevention ◽  
Greater Mekong Subregion

ABSTRACT Artemisinin-based combination therapy (ACT) is the most effective and widely used treatment for uncomplicated Plasmodium falciparum malaria and is a cornerstone for malaria control and prevention globally. Resistance to artemisinin derivatives has been confirmed in the Greater Mekong Subregion (GMS) and manifests as slow parasite clearance in patients and reduced ring stage susceptibility to artemisinins in survival assays. The P. falciparum kelch13 gene mutations associated with artemisinin-resistant parasites are now widespread in the GMS. We genotyped 277 samples collected during an observational study from 2012 to 2016 from eight provinces in Thailand to identify P. falciparum kelch13 mutations. The results were combined with previously reported genotyping results from Thailand to construct a map illustrating the evolution of P. falciparum kelch13 mutations from 2007 to 2016 in that country. Different mutant alleles were found in strains with different geographical origins. The artemisinin resistance-conferring Y493H and R539T mutations were detected mainly in eastern Thailand (bordering Cambodia), while P574L was found only in western Thailand and R561H only in northwestern Thailand. The C580Y mutation was found across the entire country and was nearing fixation along the Thai-Cambodia border. Overall, the prevalence of artemisinin resistance mutations increased over the last 10 years across Thailand, especially along the Thai-Cambodia border. Molecular surveillance and therapeutic efficacy monitoring should be intensified in the region to further assess the extent and spread of artemisinin resistance.

scholarly journals An Intramolecular Salt Bridge in Bacillus thuringiensis Cry4Ba Toxin Is Involved in the Stability of Helix α-3, Which Is Needed for Oligomerization and Insecticidal Activity

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Sabino Pacheco ◽  
Isabel Gómez ◽  
Jorge Sánchez ◽  
Blanca-Ines García-Gómez ◽  
Mario Soberón ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Double Point ◽  
Single Point ◽  
Three Dimensional ◽  
Point Mutations ◽  
Salt Bridge ◽  
Dimensional Structure ◽  
Cry Toxins ◽  
Content Type ◽  
Domain I

ABSTRACT Bacillus thuringiensis three-domain Cry toxins kill insects by forming pores in the apical membrane of larval midgut cells. Oligomerization of the toxin is an important step for pore formation. Domain I helix α-3 participates in toxin oligomerization. Here we identify an intramolecular salt bridge within helix α-3 of Cry4Ba (D111-K115) that is conserved in many members of the family of three-domain Cry toxins. Single point mutations such as D111K or K115D resulted in proteins severely affected in toxicity. These mutants were also altered in oligomerization, and the mutant K115D was more sensitive to protease digestion. The double point mutant with reversed charges, D111K-K115D, recovered both oligomerization and toxicity, suggesting that this salt bridge is highly important for conservation of the structure of helix α-3 and necessary to promote the correct oligomerization of the toxin. IMPORTANCE Domain I has been shown to be involved in oligomerization through helix α-3 in different Cry toxins, and mutations affecting oligomerization also elicit changes in toxicity. The three-dimensional structure of the Cry4Ba toxin reveals an intramolecular salt bridge in helix α-3 of domain I. Mutations that disrupt this salt bridge resulted in changes in Cry4Ba oligomerization and toxicity, while a double point reciprocal mutation that restored the salt bridge resulted in recovery of toxin oligomerization and toxicity. These data highlight the role of oligomer formation as a key step in Cry4Ba toxicity.

scholarly journals Genotypic Analysis of Genes Associated with Independent Resistance and Cross-Resistance to Isoniazid and Ethionamide in Mycobacterium tuberculosis Clinical Isolates

2015 ◽  
Vol 59 (12) ◽  
pp. 7805-7810 ◽  
Author(s):  
Johana Rueda ◽  
Teresa Realpe ◽  
Gloria Isabel Mejia ◽  
Elsa Zapata ◽  
Juan Carlos Rozo ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Multidrug Resistant ◽  
Cross Resistance ◽  
Resistance Mutations ◽  
Content Type ◽  
Genotypic Analysis ◽  
Mdr Tb ◽  
Proportion Method ◽  
Emergence Of Resistance ◽  
Phenotypic Susceptibility

ABSTRACTEthionamide (ETH) is an antibiotic used for the treatment of multidrug-resistant (MDR) tuberculosis (TB) (MDR-TB), and its use may be limited with the emergence of resistance in theMycobacterium tuberculosispopulation. ETH resistance inM. tuberculosisis phenomenon independent or cross related when accompanied with isoniazid (INH) resistance. In most cases, resistance to INH and ETH is explained by mutations in theinhApromoter and in the following genes:katG,ethA,ethR,mshA,ndh, andinhA. We sequenced the above genes in 64M. tuberculosisisolates (n= 57 ETH-resistant MDR-TB isolates;n= 3 ETH-susceptible MDR-TB isolates; andn= 4 fully susceptible isolates). Each isolate was tested for susceptibility to first- and second-line drugs using the agar proportion method. Mutations were observed in ETH-resistant MDR-TB isolates at the following rates: 100% inkatG, 72% inethA, 45.6% inmshA, 8.7% inndh, and 33.3% ininhAor its promoter. Of the three ETH-susceptible MDR-TB isolates, all showed mutations inkatG; one had a mutation inethA, and another, inmshAandinhA. Finally, of the four fully susceptible isolates, two showed no detectable mutation in the studied genes, and two had mutations inmshAgene unrelated to the resistance. Mutations not previously reported were found in theethA,mshA,katG, andndhgenes. The concordance between the phenotypic susceptibility testing to INH and ETH and the sequencing was 1 and 0.45, respectively. Among isolates exhibiting INH resistance, the high frequency of independent resistance and cross-resistance with ETH in theM. tuberculosisisolates suggests the need to confirm the susceptibility to ETH before considering it in the treatment of patients with MDR-TB.

scholarly journals Amplification ofpfmdr1,pfcrt,pvmdr1, and K13 Propeller Polymorphisms Associated with Plasmodium falciparum and Plasmodium vivax Isolates from the China-Myanmar Border

2015 ◽  
Vol 59 (5) ◽  
pp. 2554-2559 ◽  
Author(s):  
Jun Feng ◽  
Daili Zhou ◽  
Yingxue Lin ◽  
Huihui Xiao ◽  
He Yan ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Plasmodium Vivax ◽  
Vivax Malaria ◽  
Yunnan Province ◽  
Point Mutations ◽  
Border Region ◽  
Molecular Surveillance ◽  
Content Type ◽  
Antimalarial Resistance ◽  
Local Transmission

ABSTRACTMalaria in the China-Myanmar border region is still severe; local transmission of both falciparum and vivax malaria persists, and there is a risk of geographically expanding antimalarial resistance. In this research, thepfmdr1,pfcrt,pvmdr1, and K13-propeller genotypes were determined in 26Plasmodium falciparumand 64Plasmodium vivaxisolates from Yingjiang county of Yunnan province. Thepfmdr1(11.5%),pfcrt(34.6%), andpvmdr1(3.1%) mutations were prevalent at the China-Myanmar border. The indigenous samples exhibited prevalences of 14.3%, 28.6%, and 14.3% forpfmdr1N86Y,pfcrtK76T, andpfcrtM74I, respectively, whereas the samples from Myanmar showed prevalences of 10.5%, 21.1%, and 5.3%, respectively. The most prevalent genotypes ofpfmdr1andpfcrtwere Y86Y184and M74N75T76, respectively. Nopvmdr1mutation occurred in the indigenous samples but was observed in two cases coming from Myanmar. In addition, we are the first to report on 10 patients (38.5%) with five different K13 point mutations. The F446I allele is predominant (19.2%), and its prevalence was 28.6% in the indigenous samples of Yingjiang county and 15.8% in samples from Myanmar. The present data might be helpful for enrichment of the molecular surveillance of antimalarial resistance and useful for developing and updating guidance for the use of antimalarials in this region.

Identification of BCR-ABL point mutations conferring resistance to the Abl kinase inhibitor AMN107 (nilotinib) by a random mutagenesis study

Blood ◽  
2007 ◽  
Vol 109 (11) ◽  
pp. 5011-5015 ◽  
Author(s):  
Arghya Ray ◽  
Sandra W. Cowan-Jacob ◽  
Paul W. Manley ◽  
Jürgen Mestan ◽  
James D. Griffin
Keyword(s):  
Imatinib Mesylate ◽  
Kinase Inhibitor ◽  
Single Point ◽  
Point Mutations ◽  
Random Mutagenesis ◽  
Kinase Domain ◽  
Site Directed Mutagenesis ◽  
Multiple Point ◽  
Resistance Mutations ◽  
Mutagenesis Study

Abstract Patients with advanced stages of chronic myeloid leukemia (CML) often manifest imatinib mesylate resistance associated with point mutations in BCR-ABL. AMN107 is a new higher-potency inhibitor of BCR-ABL. To identify mutations in BCR-ABL that could result in resistance to AMN107, a cDNA library of BCR-ABL mutants was introduced into Ba/F3 cells followed by selection in AMN107 (0.125-0.5 μM). A total of 86 individual, drug-resistant colonies were recovered, and the SH3, SH2, and kinase domains of BCR-ABL were sequenced. A total of 46 colonies had single point mutations in BCR-ABL, with a total of 17 different mutations, all within the kinase domain. The other 40 colonies had multiple point mutations and were not analyzed further. Each of the 17 single point mutants were reconstructed by site-directed mutagenesis of native BCR-ABL and found to be approximately 2.5- to 800-fold more resistant to AMN107 than native BCR-ABL. The mutations included 6 known imatinib mesylate–resistant mutations, including T315I, which showed complete resistance to AMN107. Interestingly, most AMN107-resistant mutants were also resistant to imatinib mesylate. These results may predict some of the resistance mutations that will be detected in clinical trials with this kinase inhibitor.

scholarly journals Surveillance of Artemisinin Resistance in Plasmodium falciparum in India Using the kelch13 Molecular Marker

2015 ◽  
Vol 59 (5) ◽  
pp. 2548-2553 ◽  
Author(s):  
Neelima Mishra ◽  
Surendra Kumar Prajapati ◽  
Kamlesh Kaitholia ◽  
Ram Suresh Bharti ◽  
Bina Srivastava ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Molecular Marker ◽  
Association Studies ◽  
Point Mutations ◽  
Artemisinin Resistance ◽  
Content Type ◽  
Combination Treatments ◽  
The Status ◽  
Genome Association ◽  
Efficacy Studies

ABSTRACTMalaria treatment in Southeast Asia is threatened with the emergence of artemisinin-resistantPlasmodium falciparum. Genome association studies have strongly linked a locus onP. falciparumchromosome 13 to artemisinin resistance, and recently, mutations in the kelch13 propeller region (Pfk-13) were strongly linked to resistance. To date, this information has not been shown in Indian samples.Pfk-13mutations were assessed in samples from efficacy studies of artemisinin combination treatments in India. Samples were PCR amplified and sequenced from codon 427 to 727. Out of 384 samples, nonsynonymous mutations in the propeller region were found in four patients from the northeastern states, but their presence did not correlate with ACT treatment failures. This is the first report ofPfk-13point mutations from India. Further phenotyping and genotyping studies are required to assess the status of artemisinin resistance in this region.

scholarly journals Improved Production of a Heterologous Amylase in Saccharomyces cerevisiae by Inverse Metabolic Engineering

2014 ◽  
Vol 80 (17) ◽  
pp. 5542-5550 ◽  
Author(s):  
Zihe Liu ◽  
Lifang Liu ◽  
Tobias Österlund ◽  
Jin Hou ◽  
Mingtao Huang ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Metabolic Engineering ◽  
Secretory Pathway ◽  
Single Point ◽  
Point Mutations ◽  
Model Organisms ◽  
Cell Factory ◽  
Amylase Secretion ◽  
Content Type ◽  
Inverse Metabolic Engineering

ABSTRACTThe increasing demand for industrial enzymes and biopharmaceutical proteins relies on robust production hosts with high protein yield and productivity. Being one of the best-studied model organisms and capable of performing posttranslational modifications, the yeastSaccharomyces cerevisiaeis widely used as a cell factory for recombinant protein production. However, many recombinant proteins are produced at only 1% (or less) of the theoretical capacity due to the complexity of the secretory pathway, which has not been fully exploited. In this study, we applied the concept of inverse metabolic engineering to identify novel targets for improving protein secretion. Screening that combined UV-random mutagenesis and selection for growth on starch was performed to find mutant strains producing heterologous amylase 5-fold above the level produced by the reference strain. Genomic mutations that could be associated with higher amylase secretion were identified through whole-genome sequencing. Several single-point mutations, including an S196I point mutation in theVTA1gene coding for a protein involved in vacuolar sorting, were evaluated by introducing these to the starting strain. By applying this modification alone, the amylase secretion could be improved by 35%. As a complement to the identification of genomic variants, transcriptome analysis was also performed in order to understand on a global level the transcriptional changes associated with the improved amylase production caused by UV mutagenesis.

scholarly journals Molecular Profile of Malaria Drug Resistance Markers of Plasmodium falciparum in Suriname

2017 ◽  
Vol 61 (7) ◽  
Author(s):  
Stella M. Chenet ◽  
Sheila Akinyi Okoth ◽  
Julia Kelley ◽  
Naomi Lucchi ◽  
Curtis S. Huber ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Therapeutic Efficacy ◽  
Artemisinin Resistance ◽  
Molecular Profile ◽  
Resistance Mutations ◽  
Molecular Surveillance ◽  
Content Type ◽  
Resistance Markers ◽  
High Parasite

ABSTRACT In Suriname, an artesunate monotherapy therapeutic efficacy trial was recently conducted to evaluate partial artemisinin resistance emerging in Plasmodium falciparum. We genotyped the PfK13 propeller domain of P. falciparum in 40 samples as well as other mutations proposed to be associated with artemisinin-resistant mutants. We did not find any mutations previously associated with artemisinin resistance in Southeast Asia, but we found fixed resistance mutations for chloroquine (CQ) and sulfadoxine-pyrimethamine. Additionally, the PfCRT C350R mutation, associated with reversal of CQ resistance and piperaquine-selective pressure, was present in 62% of the samples. Our results from neutral microsatellite data also confirmed a high parasite gene flow in the Guiana Shield. Although recruiting participants for therapeutic efficacy studies is challenging in areas where malaria endemicity is very low due to the low number of malaria cases reported, conducting these studies along with molecular surveillance remains essential for the monitoring of artemisinin-resistant alleles and for the characterization of the population structure of P. falciparum in areas targeted for malaria elimination.

scholarly journals Plasmodium falciparum Genetic Diversity in Continental Equatorial Guinea before and after Introduction of Artemisinin-Based Combination Therapy

2016 ◽  
Vol 61 (1) ◽  
Author(s):  
Mónica Guerra ◽  
Rita Neres ◽  
Patrícia Salgueiro ◽  
Cristina Mendes ◽  
Nicolas Ndong-Mabale ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Drug Resistance ◽  
Plasmodium Falciparum ◽  
Combination Therapy ◽  
Microsatellite Loci ◽  
Point Mutations ◽  
Artemisinin Resistance ◽  
Equatorial Guinea ◽  
Content Type ◽  
Before And After

ABSTRACT Efforts to control malaria may affect malaria parasite genetic variability and drug resistance, the latter of which is associated with genetic events that promote mechanisms to escape drug action. The worldwide spread of drug resistance has been a major obstacle to controlling Plasmodium falciparum malaria, and thus the study of the origin and spread of associated mutations may provide some insights into the prevention of its emergence. This study reports an analysis of P. falciparum genetic diversity, focusing on antimalarial resistance-associated molecular markers in two socioeconomically different villages in mainland Equatorial Guinea. The present study took place 8 years after a previous one, allowing the analysis of results before and after the introduction of an artemisinin-based combination therapy (ACT), i.e., artesunate plus amodiaquine. Genetic diversity was assessed by analysis of the Pfmsp2 gene and neutral microsatellite loci. Pfdhps and Pfdhfr alleles associated with sulfadoxine-pyrimethamine (SP) resistance and flanking microsatellite loci were investigated, and the prevalences of drug resistance-associated point mutations of the Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps genes were estimated. Further, to monitor the use of ACT, we provide the baseline prevalences of K13 propeller mutations and Pfmdr1 copy numbers. After 8 years, noticeable differences occurred in the distribution of genotypes conferring resistance to chloroquine and SP, and the spread of mutated genotypes differed according to the setting. Regarding artemisinin resistance, although mutations reported as being linked to artemisinin resistance were not present at the time, several single nucleotide polymorphisms (SNPs) were observed in the K13 gene, suggesting that closer monitoring should be maintained to prevent the possible spread of artemisinin resistance in Africa.

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