Architecture of the mycobacterial succinate dehydrogenase with a membrane-embedded Rieske FeS cluster

Genetically Diverse Mycobacterium tuberculosis Isolates Manipulate Inflammasome and Interleukin 1β Secretion Independently of Macrophage Metabolic Rewiring

The diversity of Mycobacterium tuberculosis impacts the outcome of tuberculosis. We previously showed that M. tuberculosis isolates obtained from patients with severe disease induced low inflammasome activation and interleukin 1β (IL-1β) production by infected macrophages. Here we questioned whether this differential modulation of macrophages by M. tuberculosis isolates depended on distinct metabolic reprogramming. We found that the macrophage metabolic landscape was similar regardless of the infecting M. tuberculosis isolate. Paralleling single-Toll-like receptor (TLR) activated macrophages, glycolysis inhibition during infection impaired IL-1β secretion. However, departing from TLR -based models, in infected macrophages, IL-1β secretion was independent of mitochondrial metabolic changes and hypoxia-inducible factor 1α (HIF-1α). Additionally, we found an unappreciated impact of a host metabolic inhibitor on the pathogen, and show that inflammasome activation and IL-1β production by macrophages require metabolically active bacteria. Our study highlights the potential confounding effect of host metabolic inhibitors on the pathogen and uncoupling of M. tuberculosis-inflammasome modulation from the host metabolic reprogramming.

Structure of Mycobacterial NDH-2 Bound to a 2-Mercapto-Quinazolinone Inhibitor

Mycobacterial type II NADH dehydrogenase (NDH-2) is a promising drug target because of its central role in energy metabolism in Mycobacterium tuberculosis and other pathogens, and because it lacks a known mammalian homologue. To facilitate optimization of lead compounds, we used electron cryomicroscopy (cryo-EM) to determine the structure of NDH-2 from Mycobacterium smegmatis, a fast-growing nonpathogenic model for respiration in M. tuberculosis. The structure shows that active mycobacterial NDH-2 is dimeric, with an arrangement of monomers in the dimer that differs from the arrangement described for other prokaryotic NDH-2 dimers, instead resembling dimers formed by NDH-2 in the eukaryotes Saccharomyces cerevisiae and Plasmodium falciparum. A structure of the enzyme bound to a 2-mercapto-quinazolinone inhibitor shows that the compound interacts directly with the flavin adenine dinucleotide cofactor, blocking the menaquinone-reducing site. These results reveal structural elements of NDH-2 that could be used to design specific inhibitors of the mycobacterial enzyme.

Cryo-EM of native membranes reveals an intimate connection between the Krebs cycle and aerobic respiration in mycobacteria

To investigate the structure of the mycobacterial oxidative phosphorylation machinery, we prepared inverted membrane vesicles from Mycobacterium smegmatis, enriched for vesicles containing complexes of interest, and imaged the vesicles with electron cryomicroscopy. We show that this analysis allows determination of the structure of both mycobacterial ATP synthase and the supercomplex of respiratory complexes III and IV in their native membrane. The latter structure reveals that the enzyme malate:quinone oxidoreductase (Mqo) physically associates with the respiratory supercomplex, an interaction that is lost on extraction of the proteins from the lipid bilayer. Mqo catalyzes an essential reaction in the Krebs cycle, and in vivo survival of mycobacterial pathogens is compromised when its activity is absent. We show with high-speed spectroscopy that the Mqo:supercomplex interaction enables rapid electron transfer from malate to the supercomplex. Further, the respiratory supercomplex is necessary for malate-driven, but not NADH-driven, electron transport chain activity and oxygen consumption. Together, these findings indicate a connection between the Krebs cycle and aerobic respiration that directs electrons along a single branch of the mycobacterial electron transport chain.

Requirement of Bacillus subtilis succinate:menaquinone oxidoreductase activity for membrane energization depends on the direction of catalysis

Succinate:quinone oxidoreductases (SQR) from Bacilli catalyze reduction of menaquinone by succinate, as well as the reverse reaction. The direct activity is energetically unfavorable and lost upon ΔμН+ dissipation, thus suggesting ΔμН+ to be consumed during catalysis. Paradoxically, the generation of ΔμН+ upon fumarate reduction was never confirmed. Thus, the exact role of ΔμН+ in the operation of bacillary-type SQRs remained questionable. The purpose of this work was to clarify this issue. We have described the different operating modes of the membrane-bound SQR from Bacillus subtilis. Tightly coupled membrane vesicles from both wild-type cells and the mutant containing cytochrome bd as the only terminal oxidase were studied. This made it possible to compare the respiratory chains with 2 versus 1H+/e- stoichiometry of ΔμН+ generation. Direct and reverse activities of SQR were determined under either energized or deenergized conditions. The wild-type membranes demonstrated high succinate oxidase activity very sensitive to uncoupling. On the contrary, the mutant showed extremely low succinate oxidase activity resistant to uncoupling. ΔμН+ generation at the cost of ATP hydrolysis restored the uncoupling sensitive succinate respiration in the mutant. Membranes of the both types effectively reduced fumarate by menaquinol. This activity was not affected by energization or uncoupling, neither it was followed by ΔμН+ generation. Thus, B. subtilis SQR demonstrates two regimes: ΔμН+-coupled and not coupled. This behavior can be explained by assuming the presence of two menaquinone binding sites which drastically differ in affinity for the oxidized and reduced substrate.

Exploring the Chemical Space of Mycobacterial Oxidative Phosphorylation Inhibitors Using Molecular Modeling

Mycobacteria are opportunistic intracellular pathogens that have plagued humans and other animals throughout history and still are today. They manipulate and hijack phagocytic cells of immune systems, enabling them to occupy this peculiar infection niche. Mycobacteria exploit a plethora of mechanisms to resist antimicrobials (e. g., waxy cell walls, efflux pumps, target modification, biofilms, etc.) thereby evolving into superbugs, such as extensively drug-resistant tuberculosis (XDR TB) bacilli and the emerging pathogenic Mycobacterium abscessus complex. This review summarizes the mechanisms of action of some of the surging antimycobacterial strategies. Exploiting the fact that mycobacteria are obligate aerobes and the differences between their oxidative phosphorylation pathways versus their human counterpart opens a promising avenue for drug discovery. The polymorphism of respiratory complexes across mycobacterial pathogens imposes challenges on the repositioning of antimycobacterial agents to battle the rise in nontuberculous mycobacterial infections. In silico strategies exploiting mycobacterial respiratory machinery data to design novel therapeutic agents are touched upon. The potential druggability of mycobacterial respiratory elements is reviewed. Future research addressing the health challenges associated with mycobacterial pathogens is discussed.

Atomic-level design of biomimetic iron-sulfur clusters for biocatalysis

Designing biomimetic materials with high activity and customized biological functions by mimicking the central structure of biomolecules has become an important avenue for the development of medical materials. As an essential electron carrier, the iron-sulfur (Fe-S) clusters have the advantages of simple structure and high electron transport capacity. To rationally design and accurately construct functional materials, it is crucial to clarify the electronic structure and conformational relationships of Fe-S clusters. However, due to the complex catalytic mechanism and synthetic process in vitro, it is hard to reveal the structure-activity relationship of Fe-S clusters accurately. This review introduces the main structural types of Fe-S clusters and their catalytic mechanisms first. Then, several typical structural design strategies of biomimetic Fe-S clusters are systematically introduced. Furthermore, the development of Fe-S clusters in the biocatalytic field is enumerated, including tumor treatment, antibacterial, virus inhibition and plant photoprotection. Finally, the problems and development directions of Fe-S clusters are summarized. This review aims to guide people to accurately understand and regulate the electronic structure of Fe-S at the atomic level, which is of great significance for designing biomimetic materials with specific functions and expanding their applications in biocatalysis.

Identification of Chemical Scaffolds That Inhibit the Mycobacterium tuberculosis Respiratory Complex Succinate Dehydrogenase

Drug-resistant Mycobacterium tuberculosis is a significant cause of infectious disease morbidity and mortality for which new antimicrobials are urgently needed. Inhibitors of mycobacterial respiratory energy metabolism have emerged as promising next-generation antimicrobials, but a number of targets remain unexplored. Succinate dehydrogenase (SDH), a focal point in mycobacterial central carbon metabolism and respiratory energy production, is required for growth and survival in M. tuberculosis under a number of conditions, highlighting the potential of inhibitors targeting mycobacterial SDH enzymes. To advance SDH as a novel drug target in M. tuberculosis, we utilized a combination of biochemical screening and in-silico deep learning technologies to identify multiple chemical scaffolds capable of inhibiting mycobacterial SDH activity. Antimicrobial susceptibility assays show that lead inhibitors are bacteriostatic agents with activity against wild-type and drug-resistant strains of M. tuberculosis. Mode of action studies on lead compounds demonstrate that the specific inhibition of SDH activity dysregulates mycobacterial metabolism and respiration and results in the secretion of intracellular succinate. Interaction assays demonstrate that the chemical inhibition of SDH activity potentiates the activity of other bioenergetic inhibitors and prevents the emergence of resistance to a variety of drugs. Overall, this study shows that SDH inhibitors are promising next-generation antimicrobials against M. tuberculosis.

A dual-targeting succinate dehydrogenase and F1Fo-ATP synthase inhibitor rapidly sterilizes replicating and non-replicating Mycobacterium tuberculosis

Mycobacterial bioenergetics is a validated target space for antitubercular drug development. Here, we identify BB2-50F, a 6-substituted 5-(N,N-hexamethylene)amiloride derivative as a potent, multi-targeting bioenergetic inhibitor of Mycobacterium tuberculosis. We show that BB2-50F rapidly sterilizes both replicating and non-replicating cultures of M. tuberculosis and synergizes with several tuberculosis drugs. Target identification experiments, supported by docking studies, showed that BB2-50F targets the membrane-embedded c-ring of the F1Fo-ATP synthase and the catalytic subunit (substrate-binding site) of succinate dehydrogenase. Biochemical assays and metabolomic profiling showed that BB2-50F inhibits succinate oxidation, decreases the activity of the tricarboxylic acid (TCA) cycle, and results in succinate secretion from M. tuberculosis. Moreover, we show that the lethality of BB2-50F under aerobic conditions involves the accumulation of reactive oxygen species. Overall, this study identifies BB2-50F as an effective inhibitor of M. tuberculosis and highlights that targeting multiple components of the mycobacterial respiratory chain can produce fast-acting antimicrobials.

Acquiring of photosensitivity by Mycobacterium tuberculosis in vitro and inside infected macrophages is associated with accumulation of endogenous Zn-porphyrins

Mycobacterium tuberculosis (Mtb) is able to transition into a dormant state, causing the latent state of tuberculosis. Dormant mycobacteria acquire resistance to all known antibacterial drugs and can survive in the human body for decades before becoming active. In the dormant forms of M. tuberculosis, the synthesis of porphyrins and its Zn-complexes significantly increased when 5-aminolevulinic acid (ALA) was added to the growth medium. Transcriptome analysis revealed an activation of 8 genes involved in the metabolism of tetrapyrroles during the Mtb transition into a dormant state, which may lead to the observed accumulation of free porphyrins. Dormant Mtb viability was reduced by more than 99.99% under illumination for 30 min (300 J/cm2) with 565 nm light that correspond for Zn-porphyrin and coproporphyrin absorptions. We did not observe any PDI effect in vitro using active bacteria grown without ALA. However, after accumulation of active cells in lung macrophages and their persistence within macrophages for several days in the presence of ALA, a significant sensitivity of active Mtb cells (ca. 99.99%) to light exposure was developed. These findings create a perspective for the treatment of latent and multidrug-resistant tuberculosis by the eradication of the pathogen in order to prevent recurrence of this disease.

An evolving view of complex II-noncanonical complexes, megacomplexes, respiration, signaling, and beyond

Mitochondrial complex II is traditionally studied for its participation in two key respiratory processes: the electron transport chain and the Krebs cycle. There is now a rich body of literature explaining how complex II contributes to respiration. However, more recent research shows that not all of the pathologies associated with altered complex II activity clearly correlate with this respiratory role. Complex II activity has now been shown to be necessary for a range of biological processes peripherally related to respiration, including metabolic control, inflammation, and cell fate. Integration of findings from multiple types of studies suggests that complex II both participates in respiration and controls multiple succinate-dependent signal transduction pathways. Thus, the emerging view is that the true biological function of complex II is well beyond respiration. This review uses a semichronological approach to highlight major paradigm shifts that occurred over time. Special emphasis is given to the more recently identified functions of complex II and its subunits because these findings have infused new directions into an established field.

Structures of Tetrahymena thermophila respiratory megacomplexes on the tubular mitochondrial cristae

Tetrahymena thermophila, a classic ciliate model organism, has been shown to possess tubular mitochondrial cristae and highly divergent electron transport chain involving four transmembrane protein complexes (I-IV). Here we report cryo-EM structures of its ~8 MDa megacomplex IV₂+ (I + III₂+ II)₂, as well as a ~ 10.6 MDa megacomplex (IV₂ + I + III₂+ II)₂ at lower resolution. In megacomplex IV₂+ (I + III₂+ II)₂, each CIV₂ protomer associates one copy of supercomplex I + III₂ and one copy of CII, forming a half ring-shaped architecture that adapts to the membrane curvature of mitochondrial cristae. Megacomplex (IV₂+ I + III₂+ II)₂ defines the relative position between neighbouring half rings and maintains the proximity between CIV₂ and CIII₂ cytochrome c binding sites. Our findings expand the current understanding of divergence in eukaryotic electron transport chain organization and how it is related to mitochondrial morphology.

Structure of the human respiratory complex II

Human complex II is a key protein complex that links two essential energy-producing processes: the tricarboxylic acid cycle and oxidative phosphorylation. Deficiencies due to mutagenesis have been shown to cause mitochondrial disease and some types of cancers. However, the structure of this complex is yet to be resolved, hindering a comprehensive understanding of the functional aspects of this molecular machine. Here, we have determined the structure of human complex II in the presence of ubiquinone at 2.86 Å resolution by cryoelectron microscopy, showing it comprises two water-soluble subunits, SDHA and SDHB, and two membrane-spanning subunits, SDHC and SDHD. This structure allows us to propose a route for electron transfer. In addition, clinically relevant mutations are mapped onto the structure. This mapping provides a molecular understanding to explain why these variants have the potential to produce disease.

An update on ATP synthase inhibitors: A unique target for drug development in M. tuberculosis

ATP synthase is a key protein in the oxidative phosphorylation process, as it aids in the effective production of ATP (Adenosine triphosphate) in all life's of kingdoms. ATP synthases have distinctive properties that contribute to efficient ATP synthesis. The ATP synthase of mycobacterium is of special relevance since it has been identified as a target for potential anti-TB molecules, especially Bedaquiline (BDQ). Better knowledge of how mycobacterial ATP synthase functions and its peculiar characteristics will aid in our understanding of bacterial energy metabolism adaptations. Furthermore, identifying and understanding the important distinctions between human ATP synthase and bacterial ATP synthase may provide insight into the design and development of inhibitors that target specific ATP synthase. In recent years, many potential candidates targeting the ATP synthase of mycobacterium have been developed. In this review, we discuss the druggable targets of the Electron transport chain (ETC) and recently identified potent inhibitors (including clinical molecules) from 2015 to 2022 of diverse classes that target ATP synthase of M. tuberculosis.

Structure of mycobacterial respiratory complex I

Oxidative phosphorylation, the combined activity of the electron transport chain (ETC) and adenosine triphosphate synthase, has emerged as a valuable target for the treatment of infection by Mycobacterium tuberculosis and other mycobacteria. The mycobacterial ETC is highly branched with multiple dehydrogenases transferring electrons to a membrane-bound pool of menaquinone and multiple oxidases transferring electrons from the pool. The proton-pumping type I nicotinamide adenine dinucleotide (NADH) dehydrogenase (Complex I) is found in low abundance in the plasma membranes of mycobacteria in typical in vitro culture conditions and is often considered dispensable. We found that growth of Mycobacterium smegmatis in carbon-limited conditions greatly increased the abundance of Complex I and allowed isolation of a rotenone-sensitive preparation of the enzyme. Determination of the structure of the complex by cryoEM revealed the "orphan" two-component response regulator protein MSMEG_2064 as a subunit of the assembly. MSMEG_2064 in the complex occupies a site similar to the proposed redox-sensing subunit NDUFA9 in eukaryotic Complex I. An apparent purine nucleoside triphosphate within the NuoG subunit resembles the GTP-derived molybdenum cofactor in homologous formate dehydrogenase enzymes. The membrane region of the complex binds acyl phosphatidylinositol dimannoside, a characteristic three-tailed lipid from the mycobacterial membrane. The structure also shows menaquinone, which is preferentially used over ubiquinone by gram-positive bacteria, in two different positions along the quinone channel, comparable to ubiquinone in other structures and suggesting a conserved quinone binding mechanism.

Modular structure of complex II: An evolutionary perspective

Succinate dehydrogenases (SDHs) and fumarate reductases (FRDs) catalyse the interconversion of succinate and fumarate, a reaction highly conserved in all domains of life. The current classification of SDH/FRDs is based on the structure of the membrane anchor subunits and their cofactors. It is, however, unknown whether this classification would hold in the context of evolution. In this work, a large-scale comparative genomic analysis of complex II addresses the questions of its taxonomic distribution and phylogeny. Our findings report that for types C, D, and F, structural classification and phylogeny go hand in hand, while for types A, B and E the situation is more complex, highlighting the possibility for their classification into subgroups. Based on these findings, we proposed a revised version of the evolutionary scenario for these enzymes in which a primordial soluble module, corresponding to the cytoplasmatic subunits, would give rise to the current diversity via several independent membrane anchor attachment events.

Modified coptisine derivatives as an inhibitor against pathogenic Rhizomucor miehei, Mycolicibacterium smegmatis (Black Fungus), Monkeypox, and Marburg virus by molecular docking and molecular dynamics simulation-based drug design approach

During the second phase of SARS-CoV-2, an unknown fungal infection, identified as black fungus, was transmitted to numerous people among the hospitalized COVID-19 patients and increased the death rate. The black fungus is associated with the Mycolicibacterium smegmatis, Mucor lusitanicus, and Rhizomucor miehei microorganisms. At the same time, other pathogenic diseases, such as the Monkeypox virus and Marburg virus, impacted global health. Policymakers are concerned about these pathogens due to their severe pathogenic capabilities and rapid spread. However, no standard therapies are available to manage and treat those conditions. Since the coptisine has significant antimicrobial, antiviral, and antifungal properties; therefore, the current investigation has been designed by modifying coptisine to identify an effective drug molecule against Black fungus, Monkeypox, and Marburg virus. After designing the derivatives of coptisine, they have been optimized to get a stable molecular structure. These ligands were then subjected to molecular docking study against two vital proteins obtained from black fungal pathogens: Rhizomucor miehei (PDB ID: 4WTP) and Mycolicibacterium smegmatis (PDB ID 7D6X), and proteins found in Monkeypox virus (PDB ID: 4QWO) and Marburg virus (PDB ID 4OR8). Following molecular docking, other computational investigations, such as ADMET, QSAR, drug-likeness, quantum calculation and molecular dynamics, were also performed to determine their potentiality as antifungal and antiviral inhibitors. The docking score reported that they have strong affinities against Black fungus, Monkeypox virus, and Marburg virus. Then, the molecular dynamic simulation was conducted to determine their stability and durability in the physiological system with water at 100 ns, which documented that the mentioned drugs were stable over the simulated time. Thus, our in silico investigation provides a preliminary report that coptisine derivatives are safe and potentially effective against Black fungus, Monkeypox virus, and Marburg virus. Hence, coptisine derivatives may be a prospective candidate for developing drugs against Black fungus, Monkeypox and Marburg viruses.

Uncovering interactions between mycobacterial respiratory complexes to target drug-resistant Mycobacterium tuberculosis

Mycobacterium tuberculosis remains a leading cause of infectious disease morbidity and mortality for which new drug combination therapies are needed. Mycobacterial bioenergetics has emerged as a promising space for the development of novel therapeutics. Further to this, unique combinations of respiratory inhibitors have been shown to have synergistic or synthetic lethal interactions, suggesting that combinations of bioenergetic inhibitors could drastically shorten treatment times. Realizing the full potential of this unique target space requires an understanding of which combinations of respiratory complexes, when inhibited, have the strongest interactions and potential in a clinical setting. In this review, we discuss (i) chemical-interaction, (ii) genetic-interaction and (iii) chemical-genetic interaction studies to explore the consequences of inhibiting multiple mycobacterial respiratory components. We provide potential mechanisms to describe the basis for the strongest interactions. Finally, whilst we place an emphasis on interactions that occur with existing bioenergetic inhibitors, by highlighting interactions that occur with alternative respiratory components we envision that this information will provide a rational to further explore alternative proteins as potential drug targets and as part of unique drug combinations.

Structural Insight into Evolution of the Quinone Binding Site in Complex II

The Complex II family encompasses membrane bound succinate:quinones reductases and quinol:fumarate reductases that catalyze interconversion of succinate and fumarate coupled with reduction and oxidation of quinone. These enzymes are found in all biological genres and share a modular structure where a highly conserved soluble domain is bound to a membrane-spanning domain that is represented by distinct variations. The current classification of the complex II family members is based on the number of subunits and co-factors in the membrane anchor (types A-F). This classification also provides insights into possible evolutionary paths and suggests that some of the complex II enzymes (types A-C) co-evolved as the whole assembly. Origin of complex II types D and F may have arisen from independent events of de novo association of the conserved soluble domain with a new anchor. Here we analyze a recent structure of Mycobacterium smegmatis Sdh2, a complex II enzyme with two transmembrane subunits and two heme b molecules. This analysis supports an earlier hypothesis suggesting that mitochondrial complex II (type C) with a single heme b may have evolved as an assembled unit from an ancestor similar to M. smegmatis Sdh2.

Impaired Succinate Oxidation Prevents Growth and Influences Drug Susceptibility in Mycobacterium tuberculosis

Succinate is a major focal point in mycobacterial metabolism and respiration, serving as both an intermediate of the tricarboxylic acid (TCA) cycle and a direct electron donor for the respiratory chain. Mycobacterium tuberculosis encodes multiple enzymes predicted to be capable of catalyzing the oxidation of succinate to fumarate, including two different succinate dehydrogenases (Sdh1 and Sdh2) and a separate fumarate reductase (Frd) with possible bidirectional behavior. Previous attempts to investigate the essentiality of succinate oxidation in M. tuberculosis have relied on the use of single-gene deletion mutants, raising the possibility that the remaining enzymes could catalyze succinate oxidation in the absence of the other. To address this, we report on the use of mycobacterial CRISPR interference (CRISPRi) to construct single, double, and triple transcriptional knockdowns of sdhA1, sdhA2, and frdA in M. tuberculosis. We show that the simultaneous knockdown of sdhA1 and sdhA2 is required to prevent succinate oxidation and overcome the functional redundancy within these enzymes. Succinate oxidation was demonstrated to be essential for the optimal growth of M. tuberculosis, with the combined knockdown of sdhA1 and sdhA2 significantly impairing the activity of the respiratory chain and preventing growth on a range of carbon sources. Moreover, impaired succinate oxidation was shown to influence the activity of cell wall-targeting antibiotics and bioenergetic inhibitors against M. tuberculosis. Together, these data provide fundamental insights into mycobacterial physiology, energy metabolism, and antimicrobial susceptibility. IMPORTANCE New drugs are urgently required to combat the tuberculosis epidemic that claims 1.5 million lives annually. Inhibitors of mycobacterial energy metabolism have shown significant promise clinically; however, further advancing this nascent target space requires a more fundamental understanding of the respiratory enzymes and pathways used by Mycobacterium tuberculosis. Succinate is a major focal point in mycobacterial metabolism and respiration; yet, the essentiality of succinate oxidation and the consequences of inhibiting this process are poorly defined. In this study, we demonstrate that impaired succinate oxidation prevents the optimal growth of M. tuberculosis on a range of carbon sources and significantly reduces the activity of the electron transport chain. Moreover, we show that impaired succinate oxidation both positively and negatively influences the activity of a variety of antituberculosis drugs. Combined, these findings provide fundamental insights into mycobacterial physiology and drug susceptibility that will be useful in the continued development of bioenergetic inhibitors.

A review on enzyme complexes of electron transport chain from Mycobacterium tuberculosis as promising drug targets

Energy metabolism is a universal process occurring in all life forms. In Mycobacterium tuberculosis (Mtb), energy production is carried out in two possible ways, oxidative phosphorylation (OxPhos) and substrate-level phosphorylation. Mtb is an obligate aerobic bacterium, making it dependent on OxPhos for ATP synthesis and growth. Mtb inhabits varied micro-niches during the infection cycle, outside and within the host cells, which alters its primary metabolic pathways during the pathogenesis. In this review, we discuss cellular respiration in the context of the mechanism and structural importance of the proteins and enzyme complexes involved. These protein-protein complexes have been proven to be essential for Mtb virulence as they aid the bacteria's survival during aerobic and hypoxic conditions. ATP synthase, a crucial component of the electron transport chain, has been in the limelight, as a prominent drug target against tuberculosis. Likewise, in this review, we have explored other protein-protein complexes of the OxPhos pathway, their functional essentiality, and their mechanism in Mtb's diverse lifecycle. The review summarises crucial target proteins and reported inhibitors of the electron transport chain pathway of Mtb.