The ATP synthase of Escherichia coli: structure and function of F(0) subunits.
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.
Deckers-Hebestreit
G
G
Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, D-49069, Osnabrück, Germany. deckers-hebestreit@biologie.uni-osnabrueck.de
Greie
J
J
Stalz
W
W
Altendorf
K
K
D025181:ATP Synthetase Complexes; D004926:Escherichia coli / Q000201:enzymology*; D008565:Membrane Proteins / Q000737:chemistry; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011510:Proteolipids / Q000737:chemistry; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism
D008565:Membrane Proteins; D009097:Multienzyme Complexes; D011510:Proteolipids; C020485:proteoliposomes; D025181:ATP Synthetase Complexes; D017856:Phosphotransferases (Phosphate Group Acceptor); D006180:Proton-Translocating ATPases