The ATP synthase of Escherichia coli: structure and function of F0 subunits

Abstract

In this review we discuss recent work from our laboratory concerning the structure and/or function of the F(0) subunits of the proton-translocating ATP synthase of Escherichia coli. For the topology of subunit a a brief discussion gives (i) a detailed picture of the C-terminal two-thirds of the protein with four transmembrane helices and the C terminus exposed to the cytoplasm and (ii) an evaluation of the controversial results obtained for the localization of the N-terminal region of subunit a including its consequences on the number of transmembrane helices. The structure of membrane-bound subunit b has been determined by circular dichroism spectroscopy to be at least 75% alpha-helical. For this purpose a method was developed, which allows the determination of the structure composition of membrane proteins in proteoliposomes. Subunit b was purified to homogeneity by preparative SDS gel electrophoresis, precipitated with acetone, and redissolved in cholate-containing buffer, thereby retaining its native conformation as shown by functional coreconstitution with an ac subcomplex. Monoclonal antibodies, which have their epitopes located within the hydrophilic loop region of subunit c, and the F(1) part are bound simultaneously to the F(0) complex without an effect on the function of F(0), indicating that not all c subunits are involved in F(1) interaction. Consequences on the coupling mechanism between ATP synthesis/hydrolysis and proton translocation are discussed.

Subunit a of the F1F0 ATP Synthase Requires YidC and SecYEG for Membrane Insertion

“…However, the carboxy-and amino-terminal tails are roughly of equal length (i.e., 3.5 and 4.5 kDa, respectively). 28 Therefore, the observed 12-kDa fragment may alternatively correspond to the TMS and the C-terminus of wrongly oriented EcaN. To further explore the origin of the protease-protected 12-kDa fragment, we used an EcaN derivative (Fig.…”

Co-evolution of primordial membranes and membrane proteins

“…1(a)) are formed from alternating three α and three β subunits (B and A subunits in V-ATPases, respectively), with each of the β (A) subunits carrying an ATP/ADP-binding catalytic site [27,28,29,30,31]. The ion-translocating, membrane-spanning F O sector of simple, bacterial F-type ATPases is a complex of the integral membrane a subunit, two b subunits, and 10 to 15 small c subunits [32,79,80]. The membrane part is connected to the headpiece by two distinct stalks; the peripheral stalk consists of the protruding parts of the membrane- anchored b subunits that are connected to the α 3 β 3 hexamer via the δ subunit.…”

Biophysical Characterization of a Thermoalkaliphilic Molecular Motor with a High Stepping Torque Gives Insight into Evolutionary ATP Synthase Adaptation

“…The ␥-subunit penetrates the center of the ␣ 3 ␤ 3 catalytic hexamer at one end and is associated with the a-and c-subunits of the F 0 domain at the other end (7). The F 0 domain is composed of ab 2 c 9 -15 subunits and is membrane-bound (8). The c-subunits form a ring parallel to the membrane (9); however, although stoichiometry is fixed within a species, it is variable between species (10 -15).…”