Devanathan Raghunathan - Crosstalk along the Stalk: Dynamics of the Interaction of Subunits B and F in the A1AO ATP Synthase of Methanosarcina mazei Gö1

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        Biochemistry,    2010,    49   (19), pp 4181–4190


        The mechanism of coupling of ion pumping in the membrane-bound   AO    sector with ATP synthesis in the A3B3    headpiece of the A1    sector in the A1AO    ATP synthase is a puzzle. Previously, crosstalk between the stalk   and nucleotide-binding subunits FMm    and BMm    of theMethanosarcina   mazei   Gö1 A-ATP synthase has been observed by nucleotide-dependent   cross-link formation of both subunits inside the enzyme. The   recently determined NMR solution structure of FMm    depicts the protein as a two-domain structure, with a well-folded   N-terminus having 78 residues and a flexible C-terminal part   (residues 79−101), proposed to become structured after binding to   its partner, BMm.   Here, we detail the crucial interactions between subunits   BMm    and FMm    by determining the NMR structure of the very C-terminus of   FMm,   consisting of 20 residues and hereafter termed   FMm(81−101),   and performing molecular dynamics simulations on the resulting   structure. These data demonstrate that the flexibility of the   C-terminus enables FMm    to switch between an elongated and retracted state. Docking and   MD in conjunction with previously conducted and published NMR   results, biochemical cross-linking, and fluorescence spectroscopy   data were used to reconstruct a model of a BMm−FMmassembly.   The model of the BMm−FMm    complex shows the detailed interactions of helices 1 and 2 of the   C-terminal domain of BMm    with the C-terminal residues of FMm.   Movements of both helices of BMm    accommodate the incoming C-terminus of FMm    and connect the events of ion pumping and nucleotide binding in   the A1AO    ATP synthase.

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