title: The Fo complex of the proton-translocating F-type ATPase of Escherichia coli.
abstract: The ATP synthase (F1Fo) of Escherichia coli consists of two structurally and functionally distinct entities. The F1 part is composed of five subunits alpha, beta, gamma, delta and epsilon (3:3:1:1:1) and carries the catalytic centres of the enzyme. The membrane-bound Fo complex functions as a proton channel and consists of the three subunits a, b and c (1:2:10 +/- 1). Subunit c (8288 M(r)) exhibits a hairpin-like structure within the membrane. A conserved acidic residue (Asp-61) in the C-terminal hydrophobic segment is absolutely required for proton translocation through Fo, whereas the hydrophilic loop region is necessary for F1 binding. Expression of the chloroplast proteolipid together with subunits a and b of E. coli did not produce an active Fo hybrid complex. Therefore, the construction of hybrid c subunits consisting of parts of the proteolipid from both organisms is in progress to determine those parts of subunit c that are essential for a functional interplay with subunits a and b. Subunit a (30,276 M(r)), which is also involved in proton translocation, is an extremely hydrophobic protein with 5-8 membrane-spanning helices. Studies with alkaline phosphatase fusion proteins resulted in controversial conclusions about the localization of the N and C termini of the protein. A foreign epitope (13 amino acids) has been inserted into the N- or C-terminal region of subunit a without affecting the function of Fo. Binding studies with a monoclonal antibody against this epitope are now under investigation to determine the orientation of subunit a.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Universität Osnabrück, Fachbereich Biologie/Chemie, Arbeitsgruppe Mikrobiologie, FRG.
authors.forename: G
authors.initials: G
authors.lastname: Deckers-Hebestreit
authors.forename: K
authors.initials: K
authors.lastname: Altendorf
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics; D011522:Protons
chemical_list: D011522:Protons; D006180:Proton-Translocating ATPases