Subunit-subunit interactions and overall topology of the dimeric mitochondrial ATP synthase of Polytomella sp.

abstract Article history:Received 31 October 2009Received in revised form 15 February 2010Accepted 22 February 2010Available online 25 February 2010Keywords:Oxidative phosphorylationF 1 F 0 -ATP synthaseDimeric mitochondrial complex VChlorophycean algaeStator stalkChlamydomonas reinhardtiiPolytomella sp.ASA subunits Mitochondrial F 1 F 0 -ATP synthase of chlorophycean algae is a dimeric complex of 1600 kDa constituted by 17different subunits with varying stoichiometries, 8 of them conserved in all eukaryotes and 9 that seem to beunique to the algal lineage (subunits ASA1–9). Two different models proposing the topological assemblage ofthe nine ASA subunits in the ATP synthase of the colorless alga Polytomella sp. have been put forward. Here,we readdressed the overall topology of the enzyme with different experimental approaches: detection ofclose vicinities between subunits based on cross-linking experiments and dissociation of the enzyme intosubcomplexes, inference of subunit stoichiometry based on cysteine residue labelling, and general three-dimensional structural features of the complex as obtained from small-angle X-ray scattering and electronmicroscopy image reconstruction. Based on the available data, we refine the topological arrangement of thesubunits that constitute the mitochondrial ATP synthase of Polytomella sp.© 2010 Elsevier B.V. All rights reserved.