The diarylquinoline R207910 (TMC207) is a promising candidate in clinical development for the treatment of tuberculosis. Though R207910-resistant mycobacteria bear mutations in ATP synthase, the compound's precise target is not known. Here we establish by genetic, biochemical and binding assays that the oligomeric subunit c (AtpE) of ATP synthase is the target of R207910. Thus targeting energy metabolism is a new, promising approach for antibacterial drug discovery.

Bedaquiline (BDQ), an ATP synthase inhibitor, is the first drug to be approved for treatment of multidrug-resistant tuberculosis in decades. Though BDQ has shown excellent efficacy in clinical trials, its early bactericidal activity during the first week of chemotherapy is minimal. Here, using microfluidic devices and time-lapse microscopy of Mycobacterium tuberculosis, we confirm the absence of significant bacteriolytic activity during the first 3–4 days of exposure to BDQ. BDQ-induced inhibition of ATP synthesis leads to bacteriostasis within hours after drug addition. Transcriptional and proteomic analyses reveal that M. tuberculosis responds to BDQ by induction of the dormancy regulon and activation of ATP-generating pathways, thereby maintaining bacterial viability during initial drug exposure. BDQ-induced bacterial killing is significantly enhanced when the mycobacteria are grown on non-fermentable energy sources such as lipids (impeding ATP synthesis via glycolysis). Our results show that BDQ exposure triggers a metabolic remodelling in mycobacteria, thereby enabling transient bacterial survival.

An estimated one-third of the world population is latently infected with Mycobacterium tuberculosis. These nonreplicating, dormant bacilli are tolerant to conventional anti-tuberculosis drugs, such as isoniazid. We recently identified diarylquinoline R207910 (also called TMC207) as an inhibitor of ATP synthase with a remarkable activity against replicating mycobacteria. In the present study, we show that R207910 kills dormant bacilli as effectively as aerobically grown bacilli with the same target specificity. Despite a transcriptional down-regulation of the ATP synthase operon and significantly lower cellular ATP levels, we show that dormant mycobacteria do possess residual ATP synthase enzymatic activity. This activity is blocked by nanomolar concentrations of R207910, thereby further reducing ATP levels and causing a pronounced bactericidal effect. We conclude that this residual ATP synthase activity is indispensable for the survival of dormant mycobacteria, making it a promising drug target to tackle dormant infections. The unique dual bactericidal activity of diarylquinolines on dormant as well as replicating bacterial subpopulations distinguishes them entirely from the current anti-tuberculosis drugs and underlines the potential of R207910 to shorten tuberculosis treatment.Mycobacterium tuberculosis infection results in more than 2 million deaths per year and is the leading cause of mortality in people infected with HIV 2 (1). The global epidemic of tuberculosis (TB) is fuelled by co-infection of HIV patients with TB and a rise in multidrug-resistant TB strains (2). Despite the fact that TB control programs have been in place for decades, approximately one-third of the world population is latently infected with M. tuberculosis. Reactivation of latent TB is a high risk factor for disease development, particularly in immunocompromised individuals, such as HIV-infected patients. For global control of the TB epidemic, there is an urgent medical need for new drugs active against dormant or latent bacilli. These socalled sterilizing drugs would be able to shorten the current 6-month treatment duration for drug-susceptible TB and also offer new treatment opportunities for latent TB.Tubercle bacilli enter lungs of healthy individuals by inhalation, where they are phagocytosed by the alveolar macrophages that eliminate most of the invading mycobacteria (3). However, a small proportion of bacilli survive and exist in a nonreplicating, hypometabolic state, and these bacilli are tolerant to killing by bactericidal anti-TB drugs, such as isoniazid (4). They can linger in these altered physiological environments for an individual's lifetime and maintain the capability of causing active TB after reactivation. The pathophysiological conditions in human lesions, thought to lead to persistence, are reduced oxygen tension, nutrient limitation, and acidic pH (5, 6).Recently, we identified a new chemical class, diarylquinolines (DARQs) that demonstrate potent anti-mycobacterial activity on replicating bacilli both in vitro and...

Challenge with bedaquiline results in an electroneutral uncoupling of respiration-driven ATP synthesis. This may be a determinant of the bactericidal effects of bedaquiline, while ATP depletion may be a determinant of its delayed onset of killing. We propose that bedaquiline binds to and perturbs the a-c subunit interface of the Fo, leading to futile proton cycling, which is known to be lethal to mycobacteria.

Photosystem II (PSII) complexes, isolated from spinach and the thermophilic cyanobacterium Synechococcus elongatus, were characterized by electron microscopy and single-particle image-averaging analyses. Oxygenevolving core complexes from spinach and Synechococcus having molecular masses of about 450 kDa and dimensions of "17.2 x 9.7 nm showed twofold symmetry indicative of a dimeric organization. Confirmation of this came from image analysis of oxygen-evolving monomeric cores of PSII isolated from spinach and Synechococcus having a mass of -240 kDa.