title: Solution structure of the KdpFABC P-type ATPase from Escherichia coli by electron microscopic single particle analysis.
abstract: The K+-translocating KdpFABC complex from Escherichia coli functions as a high affinity potassium uptake system and belongs to the superfamily of P-type ATPases, although it exhibits some unique features. It comprises four subunits, and the sites of ATP hydrolysis and substrate transport are located on two different polypeptides. No structural data are so far available for elucidating the correspondingly unique mechanism of coupling ion transport and catalysis in this P-type ATPase. By use of electron microscopy and single particle analysis of negatively stained, solubilized KdpFABC complexes, we solved the structure of the complex at a resolution of 19A, which allowed us to model the arrangement of subunits within the holoenzyme and, thus, to identify the interfaces between subunits. The model showed that the K+-translocating KdpA subunit is in close contact with the transmembrane region of the ATP-hydrolyzing subunit KdpB. The cytosolic C-terminal domain of the KdpC subunit, which is assumed to play a role in cooperative ATP binding together with KdpB, is located in close vicinity to the nucleotide binding domain of KdpB. Overall, the arrangement of subunits agrees with biochemical data and the predictions on subunit interactions.
authors.affiliation: Universität Osnabrück, Fachbereich Biologie/Chemie, Arbeitsgruppe Mikrobiologie, Barbarastrabetae 11, 49069 Osnabrück, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Heitkamp
authors.forename: Bettina
authors.initials: B
authors.lastname: Böttcher
authors.forename: Jörg-Christian
authors.initials: JC
authors.lastname: Greie
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry*; D027682:Cation Transport Proteins / Q000737:chemistry*; D003198:Computer Simulation; D029968:Escherichia coli Proteins / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission / Q000379:methods*; D008958:Models, Molecular; D011188:Potassium / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; D000251:Adenosine Triphosphatases; C058166:potassium translocating Kdp-ATPase, E coli; D011188:Potassium