Inter-domain motions of the N-domain of the KdpFABC complex, a P-type ATPase, are not driven by ATP-induced conformational changes

Autor(en): Haupt, M
Bramkamp, M
Coles, M
Altendorf, K 
Kessler, H
Stichwörter: Biochemistry & Molecular Biology; CALCIUM-PUMP; CRYSTAL-STRUCTURE; ESCHERICHIA-COLI; ION-TRANSPORT; K+ transport; KDP-ATPASE; KdpB; MEMBRANE H+-ATPASE; NA,K-ATPASE; NMR; nucleotide binding; NUCLEOTIDE-BINDING DOMAIN; ORGANIZATION; P-type ATPase; SARCOPLASMIC-RETICULUM
Erscheinungsdatum: 2004
Herausgeber: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Journal: JOURNAL OF MOLECULAR BIOLOGY
Volumen: 342
Ausgabe: 5
Startseite: 1547
Seitenende: 1558
Zusammenfassung: 
P-type ATPases are involved in the active transport of ions across biological membranes. The KdpFABC complex (P-type ATPase) of Escherichia coli is a high-affinity K+ uptake system that operates only when the cell experiences osmotic stress or K+ limitation. Here, we present the solution structure of the nucleotide binding domain of KdpB (backbone RMSD 0.17 Angstrom) and a model of the AMP-PNP binding mode based on intermolecular distance restraints. The calculated AMP-PNP binding mode shows the purine ring of the nucleotide to be ``clipped'' into the binding pocket via a pi-pi-interaction to F377 on one side and a cation-pi-interaction to K395 on the other. This binding mechanism seems to be conserved in all P-type ATPases, except the heavy metal transporting ATPases (type IB). Thus, we conclude that the Kdp-ATPase (currently type IA) is misgrouped and has more similarities to type III ATPases. The KdpB N-domain is the smallest and simplest known for a P-type ATPase, and represents a minimal example of this functional unit. No evidence of significant conformational changes was observed within the N-domain upon nucleotide binding, thus ruling out a role for ATP-induced conformational changes in the reaction cycle. (C) 2004 Elsevier Ltd. All rights reserved.
ISSN: 00222836
DOI: 10.1016/j.jmb.2004.07.060

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