STRUCTURE AND ARRANGEMENT OF THE DELTA-SUBUNIT IN THE ESCHERICHIA-COLI ATP SYNTHASE (ECF1F0)

F1F0 type ATPases are made up of two parts, an F-1, which contains thr ee catalytic sites on beta subunits, and an F-0 which contains the pro ton channel. These two domains have been visualized in electron micros copy as linked by a narrow stalk of around 45 Angstrom in length. Bioc hemical studies have provided clear evidence that the gamma and epsilo n subunits are components of this stalk. There is an emerging consensu s that the gamma and epsilon subunits rotate relative to the alpha(3) beta(3) domain as part of the cooperativity and energy coupling within the complex. Two other subunits are required to link the F-1 to F-0 i n the E. coli enzyme, and these are the delta and b subunits. The stru cture of a major part of the delta subunit (residues 1-134) has now be en obtained by NMR spectroscopy. The main feature is a six alpha-helix bundle, which provides the N-terminal domain of the delta subunit. Th is domain interacts with the F-1 core via the N-terminal part of the a lpha subunit. The C-terminal domain of delta is less well defined. Thi s part is required for binding to the F-0 part by direct interaction w ith the b subunits. It is argued that delta and the two copies of the b subunit are components of a second stalk linking the F-1 and F-0 par ts, which acts as a stator to allow the energy-linked rotational movem ents of gamma and epsilon subunits. (C) 1997 Elsevier Science B.V.