PurA is the main target of aurodox, a type III secretion system inhibitor.

Anti-microbial resistance (AMR) is one of the greatest threats to global health. The continual battle between the emergence of AMR and the development of drugs will be extremely difficult to stop as long as traditional anti-biotic approaches are taken. In order to overcome this impasse, we here focused on the type III secretion system (T3SS), which is highly conserved in many Gram-negative pathogenic bacteria. The T3SS is known to be indispensable in establishing disease processes but not essential for pathogen survival. Therefore, T3SS inhibitors may be innovative anti-infective agents that could dramatically reduce the evolutionary selective pressure on strains resistant to treatment. Based on this concept, we previously identified a polyketide natural product, aurodox (AD), as a specific T3SS inhibitor using our original screening system. However, despite its promise as a unique anti-infective drug of AD, the molecular target of AD has remained unclear. In this paper, using an innovative chemistry and genetic biology-based approach, we show that AD binds to adenylosuccinate synthase (PurA), which suppresses the production of the secreted proteins from T3SS, resulting in the expression of bacterial virulence both in vitro and in vivo experiments. Our findings illuminate the potential of PurA as a target of anti-infective drugs and vaccination and could open a avenue for application of PurA in the regulation of T3SS.

Effectiveness of intravenous methylprednisolone pulse in patients with severe microscopic polyangiitis and granulomatosis with polyangiitis.

OBJECTIVES: To evaluate the effectiveness and safety of two different intravenous methylprednisolone (IVMP) pulse doses in patients with severe microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA). METHODS: We emulated a target trial using observational data from the nationwide registry in Japan. Patients with severe glomerulonephritis or diffuse alveolar haemorrhage were selected and pseudo-randomised into three groups using propensity score-based overlap weighting as follows: non-IVMP, IVMP 0.5 g/day, and IVMP 1.0 g/day. The primary outcome was all-cause death, and the secondary outcomes were composite all-cause death and kidney failure, severe relapse, and serious infection from 2 to 48 weeks after treatment initiation. To estimate the treatment effects, the Cox proportional hazard model and Fine-Gray subdistribution hazard model were used. RESULTS: In this emulated target trial, of 201 eligible patients (MPA, 175; GPA, 26), 6 (2.8%) died, 4 (2.0%) had kidney failure, 11 (5.3%) had severe relapse, and 40 (19.8%) had severe infections. Hazard ratios (HR) for IVMP 0.5 g/day and IVMP 1.0 g/day pulse groups compared with non-IVMP pulse were as follows: all-cause death = 0.46 (95% confidence interval [95%CI]: 0.07-2.81) and 0.07 (95%CI: 0.01-0.41); all-cause death/kidney failure = 1.18 (95%CI: 0.26-5.31) and 0.59 (95%CI: 0.08-4.52); subdistribution HRs for severe relapse = 1.26 (95%CI: 0.12-13.70) and 3.36 (95%CI: 0.49-23.29); and serious infection = 1.88 (95%CI: 0.76-4.65) and 0.94 (95%CI: 0.28-3.13). CONCLUSIONS: IVMP 1.0 g/day pulse may improve 48-week mortality in patients with severe MPA/GPA.

Optimal Dose of Intravenous Cyclophosphamide during remission induction therapy in ANCA-associated vasculitis: a retrospective cohort study of J-CANVAS.

OBJECTIVES: To identify the optimal dose of intravenous cyclophosphamide (IVCY) for induction therapy for anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). METHODS: We retrospectively assessed patients with AAV who received IVCY every 2-3 weeks during the remission induction phase. The associations of the IVCY dose with infection-free survival and relapse-free survival were analysed using a Cox regression model. We compared patients in three categories: very low-dose (VLD), low-dose (LD), and conventional dose (CD) (<7.5 mg/kg, 7.5-12.5 mg/kg, and >12.5 mg/kg, respectively). The non-linear association between IVCY dose and the outcomes were also evaluated. RESULTS: Of the 80 patients (median age 72 years), 12, 42, and 26 underwent the VLD, LD, and CD regimens, respectively, of whom 4, 3, and 7 developed infection or died. The adjusted hazard ratios for infection or death were 4.3 (95% confidence interval (CI) 0.94-19.8) for VLD and 5.1 (95% CI 1.21-21.3) for CD, compared with LD. We found the hazard ratio for infection or death increased when the initial IVCY dose exceeded 9 mg/kg. Relapse-free survival did not differ clearly. CONCLUSION: Low-dose IVCY (7.5-12.5 mg/kg) may result in fewer infections and similar relapse rates compared with the conventional regimen (>12.5 mg/kg).

An AsCas12f-based compact genome-editing tool derived by deep mutational scanning and structural analysis.

SpCas9 and AsCas12a are widely utilized as genome-editing tools in human cells. However, their relatively large size poses a limitation for delivery by cargo-size-limited adeno-associated virus (AAV) vectors. The type V-F Cas12f from Acidibacillus sulfuroxidans is exceptionally compact (422 amino acids) and has been harnessed as a compact genome-editing tool. Here, we developed an approach, combining deep mutational scanning and structure-informed design, to successfully generate two AsCas12f activity-enhanced (enAsCas12f) variants. Remarkably, the enAsCas12f variants exhibited genome-editing activities in human cells comparable with those of SpCas9 and AsCas12a. The cryoelectron microscopy (cryo-EM) structures revealed that the mutations stabilize the dimer formation and reinforce interactions with nucleic acids to enhance their DNA cleavage activities. Moreover, enAsCas12f packaged with partner genes in an all-in-one AAV vector exhibited efficient knock-in/knock-out activities and transcriptional activation in mice. Taken together, enAsCas12f variants could offer a minimal genome-editing platform for in vivo gene therapy.

Mechanistic and evolutionary insights into a type V-M CRISPR-Cas effector enzyme.

RNA-guided type V CRISPR-Cas12 effectors provide adaptive immunity against mobile genetic elements (MGEs) in bacteria and archaea. Among diverse Cas12 enzymes, the recently identified Cas12m2 (CRISPR-Cas type V-M) is highly compact and has a unique RuvC active site. Although the non-canonical RuvC triad does not permit dsDNA cleavage, Cas12m2 still protects against invading MGEs through transcriptional silencing by strong DNA binding. However, the molecular mechanism of RNA-guided genome inactivation by Cas12m2 remains unknown. Here we report cryo-electron microscopy structures of two states of Cas12m2-CRISPR RNA (crRNA)-target DNA ternary complexes and the Cas12m2-crRNA binary complex, revealing structural dynamics during crRNA-target DNA heteroduplex formation. The structures indicate that the non-target DNA strand is tightly bound to a unique arginine-rich cluster in the recognition (REC) domains and the non-canonical active site in the RuvC domain, ensuring strong DNA-binding affinity of Cas12m2. Furthermore, a structural comparison of Cas12m2 with TnpB, a putative ancestor of Cas12 enzymes, suggests that the interaction of the characteristic coiled-coil REC2 insertion with the protospacer-adjacent motif-distal region of the heteroduplex is crucial for Cas12m2 to engage in adaptive immunity. Collectively, our findings improve mechanistic understanding of diverse type V CRISPR-Cas effectors and provide insights into the evolution of TnpB to Cas12 enzymes.

Seasonal Influence on Development of Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A Retrospective Cohort Study Conducted at Multiple Institutions in Japan (J-CANVAS).

OBJECTIVE: To clarify seasonal and other environmental effects on the onset of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). METHODS: We enrolled patients with new-onset eosinophilic granulomatosis with polyangiitis (EGPA), microscopic polyangiitis (MPA), and granulomatosis with polyangiitis (GPA) registered in the database of a Japanese multicenter cohort study. We investigated the relationship between environmental factors and clinical characteristics. Seasons were divided into 4 (spring, summer, autumn, and winter), and the seasonal differences in AAV onset were analyzed using Pearson chi-square test, with an expected probability of 25% for each season. RESULTS: A total of 454 patients were enrolled, with a mean age of 70.9 years and a female proportion of 55.5%. Overall, 74, 291, and 89 patients were classified as having EGPA, MPA, and GPA, respectively. Positivity for myeloperoxidase (MPO)-ANCA and proteinase 3 (PR3)-ANCA was observed in 355 and 46 patients, respectively. Overall, the seasonality of AAV onset significantly deviated from the expected 25% for each season (P = 0.001), and its onset was less frequently observed in autumn. In ANCA serotypes, seasonality was significant in patients with MPO-ANCA (P < 0.001), but not in those with PR3-ANCA (P = 0.97). Additionally, rural residency of patients with AAV was associated with PR3-ANCA positivity and biopsy-proven pulmonary vasculitis. CONCLUSION: The onset of AAV was influenced by seasonal variations and was less frequently observed in autumn. In contrast, the occurrence of PR3-ANCA was triggered, not by season, but by rural residency.

Prophylactic administration of ivermectin attenuates SARS-CoV-2 induced disease in a Syrian Hamster Model.

COVID-19, caused by SARS-CoV-2 infection, is currently among the most important public health concerns worldwide. Although several effective vaccines have been developed, there is an urgent clinical need for effective pharmaceutical treatments for treatment of COVID-19. Ivermectin, a chemical derivative of avermectin produced by Streptomyces avermitilis, is a macrocyclic lactone with antiparasitic activity. Recent studies have shown that ivermectin inhibits SARS-CoV-2 replication in vitro. In the present study, we investigated the in vivo effects of ivermectin in a hamster model of SARS-CoV-2 infection. The results of the present study demonstrate oral administration of ivermectin prior to SARS-CoV-2 infection in hamsters was associated with decreased weight loss and pulmonary inflammation. In addition, the administration of ivermectin reduced pulmonary viral titers and mRNA expression level of pro-inflammatory cytokines associated with severe COVID-19 disease. The administration of ivermectin rapidly induced the production of virus-specific neutralizing antibodies in the late stage of viral infection. Zinc concentrations leading to immune quiescence were also significantly higher in the lungs of ivermectin-treated hamsters compared to controls. These results indicate that ivermectin may have efficacy in reducing the development and severity of COVID-19 by affecting host immunity in a hamster model of SARS-CoV-2 infection.

Cryo-EM structure of the transposon-associated TnpB enzyme.

The class 2 type V CRISPR effector Cas12 is thought to have evolved from the IS200/IS605 superfamily of transposon-associated TnpB proteins1. Recent studies have identified TnpB proteins as miniature RNA-guided DNA endonucleases2,3. TnpB associates with a single, long RNA (ωRNA) and cleaves double-stranded DNA targets complementary to the ωRNA guide. However, the RNA-guided DNA cleavage mechanism of TnpB and its evolutionary relationship with Cas12 enzymes remain unknown. Here we report the cryo-electron microscopy (cryo-EM) structure of Deinococcus radiodurans ISDra2 TnpB in complex with its cognate ωRNA and target DNA. In the structure, the ωRNA adopts an unexpected architecture and forms a pseudoknot, which is conserved among all guide RNAs of Cas12 enzymes. Furthermore, the structure, along with our functional analysis, reveals how the compact TnpB recognizes the ωRNA and cleaves target DNA complementary to the guide. A structural comparison of TnpB with Cas12 enzymes suggests that CRISPR-Cas12 effectors acquired an ability to recognize the protospacer-adjacent motif-distal end of the guide RNA-target DNA heteroduplex, by either asymmetric dimer formation or diverse REC2 insertions, enabling engagement in CRISPR-Cas adaptive immunity. Collectively, our findings provide mechanistic insights into TnpB function and advance our understanding of the evolution from transposon-encoded TnpB proteins to CRISPR-Cas12 effectors.

Association between hypogammaglobulinaemia and severe infections during induction therapy in ANCA-associated vasculitis: from J-CANVAS study.

OBJECTIVES: To investigate the association between decreased serum IgG levels caused by remission-induction immunosuppressive therapy of antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and the development of severe infections. METHODS: We conducted a retrospective cohort study of patients with new-onset or severe relapsing AAV enrolled in the J-CANVAS registry, which was established at 24 referral sites in Japan. The minimum serum IgG levels up to 24 weeks and the incidence of severe infection up to 48 weeks after treatment initiation were evaluated. After multiple imputations for all explanatory variables, we performed the multivariate analysis using a Fine-Gray model to assess the association between low IgG (the minimum IgG levels <500 mg/dl) and severe infections. In addition, the association was expressed as a restricted cubic spline (RCS) and analysed by treatment subgroups. RESULTS: Of 657 included patients (microscopic polyangiitis, 392; granulomatosis with polyangiitis, 139; eosinophilic granulomatosis with polyangiitis, 126), 111 (16.9%) developed severe infections. The minimum serum IgG levels were measured in 510 patients, of whom 77 (15.1%) had low IgG. After multiple imputations, the confounder-adjusted hazard ratio of low IgG for the incidence of severe infections was 1.75 (95% confidence interval: 1.03-3.00). The RCS revealed a U-shaped association between serum IgG levels and the incidence of severe infection with serum IgG 946 mg/dl as the lowest point. Subgroup analysis showed no obvious heterogeneity between treatment regimens. CONCLUSION: Regardless of treatment regimens, low IgG after remission-induction treatment was associated with the development of severe infections up to 48 weeks after treatment initiation.

Association between early immunophenotypic changes and therapeutic response of belimumab in patients with systemic lupus erythematosus.

Belimumab is a therapeutic medication that inhibits the B-cell-activating factor (BAFF) used for systemic lupus erythematosus (SLE); however, the response sometimes varies among individuals, even when patients are stratified based on general clinical characteristics. Therefore, we focused on immunological phenotypic changes with belimumab, investigated their association with subsequent clinical courses, and sought to identify relevant immunological indicators to stratify patients who would benefit from belimumab. We assessed changes in B and T cell phenotypes, as well as BAFF-related factors, such as levels of BAFF and a proliferation-inducing ligand, and expression of three BAFF receptors: BAFF receptor (BAFF-R), B-cell maturation antigen (BCMA), transmembrane activator and cyclophilin ligand interactor (TACI), in 19 patients with SLE who were treated with belimumab before and 3 months after treatment. First, to visualize patterns in complex and diverse data, we summarized B cell changes such as subsets and BAFF receptor expressions into two axes, the first and second principal components (PC1 and PC2), and characterized broad phenotypic changes by cluster analysis. Next, we evaluated whether the B cell changes represented by PC1 and PC2 were associated with other concurrent phenotypic changes, baseline factors, and treatment response at 6 months. We found that lower PC2, indicating increased BAFF-R expression and decreased percentage of naïve B cells, was associated with a subsequent therapeutic response at 6 months (odds ratio 5.3, 95% confidence interval 1.2-24, p = .031). Furthermore, higher percentages of effector memory CD3+CD4+ T cells at baseline were associated with lower PC2 and therapeutic response. Further analysis revealed that increased PC1, as reflected by increased BCMA and TACI expression and an increase in the percentage of class-switched memory B cells, was associated with both T and B cell activation. Although belimumab is a B-cell targeted therapy, it can also influence T-cell phenotypes. Thus, early B cell changes could be used to predict treatment response, and their changes could be predicted from baseline T cell phenotypes, indicating the importance of B and T cell interactions.

New nitrogen-compounds, penicidones E and F, produced by the fungal strain Oidiodendron sp. FKI-7498.

The nitrogen rule in mass spectrometry was used to search for new nitrogen-compounds from microbial metabolites. During this program, two new nitrogen-containing compounds, penicidones E and F, were discovered from the filamentous fungal strain FKI-7498, which was isolated from soil collected in Tokushima, Japan, and identified as Oidiodendron sp. by sequence analysis of the internal transcribed spacer region, including 5.8S ribosomal RNA. The structures of penicidones E and F were determined by mass spectrometry, nuclear magnetic resonance spectroscopy, and chemical modification analyses. These analyses revealed that penicidones E and F have a core structure of 3,5-dihydroxy-2-(4-pyridone-3-carbonyl)benzoic acid. Penicidone E exhibited hydroxyl radical scavenging activity.

Detection and characterization of new mangromicin analogs by tandem mass spectrometry.

Many useful natural products are usually screened based on their biological activities. On the other hand, various natural products can be detected based on their physicochemical properties. We have already reported the isolation and characterization of mangromicins from a cultural broth of Lechevalieria aerocolonigenes K10-0216 using physicochemical screening. In this report, we have conducted the mass spectrometry-based screening of new mangromicin analogs based on the neutral loss pattern originated from the unique cyclopentadecane skeleton of mangromicins. Two novel analogs were detected showing characteristic neutral loss pattern found in eight known mangromicin analogs. We propose the structures of the newly-found analogs based on the mass spectrometric as well as genomic and metabolic pathway data.

Hypertrophic pachymeningitis in ANCA-associated vasculitis: a cross-sectional and multi-institutional study in Japan (J-CANVAS).

BACKGROUND: This study investigated the characteristics of hypertrophic pachymeningitis (HP) in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), using information from a multicenter study in Japan. METHODS: We analyzed the clinical information of 663 Asian patients with AAV (total AAV), including 558 patients with newly diagnosed AAV and 105 with relapsed AAV. Clinical findings were compared between patients with and without HP. To elucidate the relevant manifestations for HP development, multivariable logistic regression analyses were additionally performed. RESULTS: Of the patients with AAV (mean age, 70.2 ± 13.5 years), HP was noted in 30 (4.52%), including 20 (3.58%) with newly diagnosed AAV and 10 (9.52%) with relapsed AAV. Granulomatosis with polyangiitis (GPA) was classified in 50% of patients with HP. A higher prevalence of GPA was significantly observed in patients with HP than in those without HP in total AAV and newly diagnosed AAV (p < 0.001). In newly diagnosed AAV, serum proteinase 3 (PR3)-ANCA positivity was significantly higher in patients with HP than in those without HP (p = 0.030). Patients with HP significantly had ear, nose, and throat (ENT) (odds ratio [OR] 1.48, 95% confidence interval [CI] 1.03-2.14, p = 0.033) and mucous membrane/eye manifestations (OR 5.99, 95% CI 2.59-13.86, p < 0.0001) in total AAV. Moreover, they significantly had conductive hearing loss (OR 11.6, 95% CI 4.51-29.57, p < 0.0001) and sudden visual loss (OR 20.9, 95% CI 5.24-85.03, p < 0.0001). CONCLUSION: GPA was predominantly observed in patients with HP. Furthermore, in newly diagnosed AAV, patients with HP showed significantly higher PR3-ANCA positivity than those without HP. The ear and eye manifestations may be implicated in HP development.

Siccanin Is a Dual-Target Inhibitor of Plasmodium falciparum Mitochondrial Complex II and Complex III.

Plasmodium falciparum contains several mitochondrial electron transport chain (ETC) dehydrogenases shuttling electrons from the respective substrates to the ubiquinone pool, from which electrons are consecutively transferred to complex III, complex IV, and finally to the molecular oxygen. The antimalarial drug atovaquone inhibits complex III and validates this parasite's ETC as an attractive target for chemotherapy. Among the ETC dehydrogenases from P. falciparum, dihydroorotate dehydrogenase, an essential enzyme used in de novo pyrimidine biosynthesis, and complex III are the two enzymes that have been characterized and validated as drug targets in the blood-stage parasite, while complex II has been shown to be essential for parasite survival in the mosquito stage; therefore, these enzymes and complex II are considered candidate drug targets for blocking parasite transmission. In this study, we identified siccanin as the first (to our knowledge) nanomolar inhibitor of the P. falciparum complex II. Moreover, we demonstrated that siccanin also inhibits complex III in the low-micromolar range. Siccanin did not inhibit the corresponding complexes from mammalian mitochondria even at high concentrations. Siccanin inhibited the growth of P. falciparum with IC50 of 8.4 µM. However, the growth inhibition of the P. falciparum blood stage did not correlate with ETC inhibition, as demonstrated by lack of resistance to siccanin in the yDHODH-3D7 (EC50 = 10.26 µM) and Dd2-ELQ300 strains (EC50 = 18.70 µM), suggesting a third mechanism of action that is unrelated to mitochondrial ETC inhibition. Hence, siccanin has at least a dual mechanism of action, being the first potent and selective inhibitor of P. falciparum complexes II and III over mammalian enzymes and so is a potential candidate for the development of a new class of antimalarial drugs.

Semisynthesis of Antitrypanosomal p-Quinone Analog Possesing the Komaroviquinone Pharmacophore.

A p-quinone analog having the komaroviquinone pharmacophore fused with a more conformationally flexible cycloheptane ring, was semisynthesized from natural demethlsalvicanol isolated from Perovskia abrotanoides via four steps in 26% overall yield. The IC50 for the antitrypanosomal activity of the analog was 0.55 µM.

Afidopyropen, a novel insecticide originating from microbial secondary extracts.

Afidopyropen, a novel insecticide, is a derivative of pyripyropene A, which is produced by the filamentous fungus Penicillium coprobium. Afidopyropen has strong insecticidal activity against aphids and is currently used as a control agent of sucking pests worldwide. In this study, we summarized the biological properties and field efficacies of its derivatives against agricultural pests using official field trials conducted in Japan. Afidopyropen showed good residual efficacies against a variety of aphids, whiteflies and other sucking pests under field conditions. Furthermore, toxicological studies revealed its safety profiles against nontarget organisms, such as the honeybee, natural enemies and other beneficial insects, as well as mammals. Thus, afidopyropen is a next-generation agrochemical for crop protection that has a low environmental impact.

Trehangelins ameliorate inflammation-induced skin senescence by suppressing the epidermal YAP-CCN1 axis.

Trehangelins (THG) are newly identified trehalose compounds derived from broth cultures of an endophytic actinomycete, Polymorphospora rubra. THG are known to suppress Cellular Communication Network factor 1 (CCN1), which regulates collagen homeostasis in the dermis. Although the physical properties of THG suggest a high penetration of the stratum corneum, the effect of THG on the epidermis has not been reported. Here we describe a possible mechanism involved in skin aging focusing on the effect of THG on epidermal CCN1. This study shows that: (1) THG suppress epidermal CCN1 expression by inhibiting the translocation of Yes-Associated Protein (YAP) to nuclei. (2) Epidermal CCN1, localized at the basement membrane, regulates the balance between the growth and differentiation of keratinocytes. (3) Keratinocytes secrete more CCN1 than fibroblasts, which leads to disruption of the basement membrane and extracellular matrix components. (4) The secretion of CCN1 from keratinocytes is increased by ultraviolet B exposure, especially in aged keratinocytes, and deteriorates the elastic fiber structures in the underlying dermis. (5) Topical application of THG ameliorates the structure of the basement membrane in ex vivo human skin explants. Taken together, THG might be a promising treatment for aged skin by suppressing the aberrant YAP-CCN1 axis.

Risk of adrenal insufficiency in patients with polymyalgia rheumatica versus patients with rheumatoid arthritis: A cross-sectional study.

OBJECTIVE: To determine whether patients with polymyalgia rheumatica (PMR) are more susceptible to glucocorticoid-induced adrenal insufficiency, one of the barriers to glucocorticoid tapering strategies, compared to patients with rheumatoid arthritis (RA). METHODS: This cross-sectional study included PMR and RA patients who underwent adrenocorticotropic hormone (ACTH) tests to assess adrenal function. The eligibility criteria were as follows: previous use of prednisolone (PSL) ≥ 5 mg/day, use of PSL for six consecutive months before ACTH test, and current use of PSL at 5 mg/day or less. The association between disease type (PMR vs. RA) and insufficient adrenal response was assessed using logistic regression models. RESULTS: Twenty-six of 34 (76.5%) patients with PMR and 13 of 37 (35.1%) patients with RA had insufficient adrenal response. Compared to patients with RA, patients with PMR were more likely to have insufficient adrenal response, even after adjusting for age, sex, and PSL dose (adjusted odds ratio, 6.75; 95% confidence interval, 1.78-25.60). CONCLUSION: Patients with PMR have a higher risk of glucocorticoid-induced adrenal insufficiency than patients with RA. Assessing the adrenal function in patients with PMR will contribute to establishing a more appropriate glucocorticoid reduction strategy.

Traminines A and B, produced by Fusarium concentricum, inhibit oxidative phosphorylation in Saccharomyces cerevisiae mitochondria.

Two new tetramic acid derivatives, traminines A (1) and B (2), were isolated from a culture broth of Fusarium concentricum FKI-7550 by bioassay-guided fractionation using multidrug-sensitive Saccharomyces cerevisiae 12geneΔ0HSR-iERG6. The chemical structures of 1 and 2 were elucidated by NMR studies. Compounds 1 and 2 inhibited the growth of the multidrug-sensitive yeast strain on nonfermentable medium containing glycerol, but not on fermentable medium containing glucose. These results strongly suggest that they target mitochondrial machineries presiding over ATP production via oxidative phosphorylation. Throughout the assay monitoring overall ADP-uptake/ATP-release in yeast mitochondria, 1 and 2 were shown to inhibit one or more enzymes involving oxidative phosphorylation. Based on biochemical characterization, we found that the interference with oxidative phosphorylation by 1 is attributable to the dual inhibition of complex III and FoF1-ATPase, whereas that by 2 is solely due to the inhibition of complex III.