SMALL-ANGLE NEUTRON-SCATTERING FROM THE RECONSTITUTED TF1 OF H+-ATPASE FROM THERMOPHILIC BACTERIUM-PS3 WITH DEUTERATED SUBUNITS

Subunits α, β and γ of adenosine triphosphatase (H+-ATPase) from the thermophilic bacterium PS3 (TF1) have been over-expressed in Escherichia coli. α and β subunits deuterated to the level of 90% were obtained by culturing E. coli in 2H2O medium. Both the subunits and the reconstituted αβγ complex, TF1, which contain the deuterated components in various combinations, were studied in solution by small-angle neutron scattering. The individual shapes of the subunits and their organization in the αβγ-TF1 complex were examined using the techniques of selective deuteration and contrast variation. The α and β subunits are well approximated as ellipsoids of revolution having minor semiaxes of 20·4(±0·4) and 20·0(±0·2) Å, and major semi-axes of 53·0(±1·4) and 55·8(±0·9) Å, respectively. In the TF1 complex, three β subunits are aligned to form an equilateral triangle, with their major axes tilted by 35° with respect to the 3-fold axis of the complex. The β-β distance is about 53 Å. Three α subunits are similarly arranged, positioned between the β subunits, and with their direction of tilt opposite to that of the β subunits. The centers of the α and β subunits lie in the same plane, forming a hexagon. Adjacent subunits overlap in this model, suggesting that they are not simple ellipsoids of revolution. © 1990 Academic Press Limited.