The c13 Ring from a Thermoalkaliphilic ATP Synthase Reveals an Extended Diameter Due to a Special Structural Region |
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Authors: | Doreen Matthies Laura Preiss Adriana L Klyszejko Gregory M Cook Thomas Meier |
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Institution: | 1 Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany 2 Biotechnology Center, University of Technology Dresden, Tatzberg 47, 01307 Dresden, Germany 3 Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand 4 Cluster of Excellence Macromolecular Complexes, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany |
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Abstract: | We have structurally characterized the c-ring from the thermoalkaliphilic Bacillus sp. strain TA2.A1 F1Fo-ATP synthase. Atomic force microscopy imaging and cryo-electron microscopy analyses confirm previous mass spectrometric data indicating that this c-ring contains 13 c-subunits. The cryo-electron microscopy map obtained from two-dimensional crystals shows less closely packed helices in the inner ring compared to those of Na+-binding c11 rings. The inner ring of α-helices in c11 rings harbors a conserved GxGxGxGxG motif, with glycines located at the interface between c-subunits, which is responsible for the close packing of these helices. This glycine motif is altered in the c13 ring of Bacillus sp. strain TA2.A1 to AxGxSxGxS, leading to a change in c-c subunit contacts and thereby enlarging the c-ring diameter to host a greater number of c-subunits. An altered glycine motif is a typical feature of c-subunit sequences in alkaliphilic Bacillus species. We propose that enlarged c-rings in proton-dependent F-ATP synthases may represent an adaptation to facilitate ATP synthesis at low overall proton-motive force, as occurs in bacteria that grow at alkaline pH. |
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Keywords: | AFM atomic force microscopy 2D two-dimensional EM electron microscopy |
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