Structure and function of Mycobacterium-specific components of F-ATP synthase subunits α and ε.

Graphical abstract Highlights • 3D reconstruction from electron micrographs of the α chi 3 :β 3 :γ complex. • Low resolution solution structure of the mycobacterial F-ATP synthase subunit α. • Critical residues of subunit ε for energy coupling of mycobacterial F-ATP synthase. • Residue 121 of mycobacterial subunit ε affects MgADP inhibition. • Differences of the N-terminus of mycobacterial ε to its prokaryotic counterparts. Abstract The Mycobacterium tuberculosis (Mtb) F 1 F O -ATP synthase (α 3 :β 3 :γ:δ:ε: a : b : b' : c 9) is an essential enzyme that supplies energy for both the aerobic growing and the hypoxic dormant stage of the mycobacterial life cycle. Employing the heterologous F-ATP synthase model system α chi 3 :β 3 :γ we showed previously, that transfer of the C-terminal domain (CTD) of Mtb subunit α (Mt α 514-549) to a standard F-ATP synthase α subunit suppresses ATPase activity. Here we determined the 3D reconstruction from electron micrographs of the α chi 3 :β 3 :γ complex reconstituted with the Mtb subunit ε (Mt ε), which has been shown to crosstalk with the CTD of Mt α. Together with the first solution shape of Mtb subunit α (Mt α), derived from solution X-ray scattering, the structural data visualize the extended C-terminal stretch of the mycobacterial subunit α. In addition, Mt ε mutants Mt εR62L, Mt εE87A, Mt ε 6-121 , and Mt ε 1-120 , reconstituted with α chi 3 :β 3 :γ provided insight into their role in coupling and in trapping inhibiting MgADP. NMR solution studies of Mt εE87A gave insights into how this residue contributes to stability and crosstalk between the N-terminal domain (NTD) and the CTD of Mt ε. Analyses of the N-terminal mutant Mt ε 6-121 highlight the differences of the NTD of mycobacterial subunit ε to the well described Geobacillus stearothermophilus or Escherichia coli counterparts. These data are discussed in context of a crosstalk between the very N-terminal amino acids of Mt ε and the loop region of one c subunit of the c -ring turbine for coupling of proton-translocation and ATP synthesis activity. [ABSTRACT FROM AUTHOR]