title: A structural analysis of asymmetry required for catalytic activity of an ABC-ATPase domain dimer.
abstract: The ATP-binding cassette (ABC)-transporter haemolysin (Hly)B, a central element of a Type I secretion machinery, acts in concert with two additional proteins in Escherichia coli to translocate the toxin HlyA directly from the cytoplasm to the exterior. The basic set of crystal structures necessary to describe the catalytic cycle of the isolated HlyB-NBD (nucleotide-binding domain) has now been completed. This allowed a detailed analysis with respect to hinge regions, functionally important key residues and potential energy storage devices that revealed many novel features. These include a structural asymmetry within the ATP dimer that was significantly enhanced in the presence of Mg2+, indicating a possible functional asymmetry in the form of one open and one closed phosphate exit tunnel. Guided by the structural analysis, we identified two amino acids, closing one tunnel by an apparent salt bridge. Mutation of these residues abolished ATP-dependent cooperativity of the NBDs. The implications of these new findings for the coupling of ATP binding and hydrolysis to functional activity are discussed.
authors.affiliation: Institute of Biochemistry, Heinrich Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Jelena
authors.initials: J
authors.lastname: Zaitseva
authors.forename: Christine
authors.initials: C
authors.lastname: Oswald
authors.forename: Thorsten
authors.initials: T
authors.lastname: Jumpertz
authors.forename: Stefan
authors.initials: S
authors.lastname: Jenewein
authors.forename: Alexander
authors.initials: A
authors.lastname: Wiedenmann
authors.forename: I Barry
authors.initials: IB
authors.lastname: Holland
authors.forename: Lutz
authors.initials: L
authors.lastname: Schmitt
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D020816:Amino Acid Motifs; D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D017124:Conserved Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology*; D006460:Hemolysin Proteins; D017434:Protein Structure, Tertiary / Q000235:genetics
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D006460:Hemolysin Proteins; C050837:Hlyb protein, Bacteria; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases