title: The topology of the proton translocating F0 component of the ATP synthase from E. coli K12: studies with proteases.
abstract: The accessibility of the three F0 subunits a, b and c from the Escherichia coli K12 ATP synthase to various proteases was studied in F1-depleted inverted membrane vesicles. Subunit b was very sensitive to all applied proteases. Chymotrypsin produced a defined fragment of mol. wt. 15,000 which remained tightly bound to the membrane. The cleavage site was located at the C-terminal region of subunit b. Larger amounts of proteases were necessary to attack subunit a (mol. wt. 30,000). There was no detectable cleavage of subunit c. It is suggested that the major hydrophilic part of subunit b extends from the membrane into the cytoplasm and is in contact with the F1 sector. The F1 sector was found to afford some protection against proteolysis of the b subunit in vitro and in vivo. Protease digestion had no influence on the electro-impelled H+ conduction via F0 but ATP-dependent H+ translocation could not be reconstituted upon binding of F1. A possible role for subunit b as a linker between catalytic events on the F1 component and the proton pathway across the membrane is discussed.
authors.affiliation: Department of Stoffwechselregulation, GBF-Gesellschaft für Biotechnologische Forschung mbH., Braunschweig-Stöckheim, FRG.
authors.forename: J
authors.initials: J
authors.lastname: Hoppe
authors.forename: P
authors.initials: P
authors.lastname: Friedl
authors.forename: H U
authors.initials: HU
authors.lastname: Schairer
authors.forename: W
authors.initials: W
authors.lastname: Sebald
authors.forename: K
authors.initials: K
authors.lastname: von Meyenburg
authors.forename: B B
authors.initials: BB
authors.lastname: Jørgensen
mesh_terms: D025243:Bacterial Proton-Translocating ATPases / Q000378:metabolism*; D002918:Chymotrypsin / Q000378:metabolism; D011522:Protons; D020860:Subtilisin / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D011522:Protons; D002918:Chymotrypsin; D014357:Trypsin; D020860:Subtilisin; D025243:Bacterial Proton-Translocating ATPases