Aerobic organisms obtain energy by linking electron transfer from NADH to O 2 , through the respiratory chain, to transmembrane proton translocation. In mycobacteria the respiratory chain is branched; the membrane-bound electron carrier menaquinol (MQH 2 ) donates electrons either to the O 2 -reducing cytochrome bd or a supercomplex that is composed of a complex (C) III 2 dimer flanked by two CIVs. Here, we measured the dimethyl-naphthoquinone (DMNQH 2, a menaquinol analogue) oxidation:O 2 reduction activities of the CIII 2 CIV 2 supercomplex and cytochrome bd in the presence of an analogue (decylubiquinone, DCQ) of the mammalian electron carrier, ubiquinol. The data show that DCQH 2 inhibits both the CIII 2 CIV 2 and cytochrome bd activities, suggesting that DCQ/DCQH 2 interferes with both branches of the respiratory chain. Cryo-EM data of the M. smegmatis supercomplex shows that oxidized DCQ binds in the electron donor site (Q o ) of CIII 2 . Accordingly, growth of M. smegmatis cells was impaired in the presence of DCQ. Remarkably, DCQ also impairs intracellular growth of virulent M. tuberculosis cells in human primary macrophages suggesting that the compound could potentially be used as an adjuvant during tuberculosis disease treatment.
Organizational Affiliation:
Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden.
Division of Medical Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
Center for Infectious Medicine (CIM), Department of Medicine Huddinge, Karolinska Institutet, ANA Futura, Huddinge, Sweden.
Center for Infectious Medicine (CIM), Department of Medicine Huddinge, Karolinska Institutet, ANA Futura, Huddinge, Sweden. susanna.brighenti@ki.se.
Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden. peterb@dbb.su.se.
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