Inter-domain motions of the N-domain of the KdpFABC complex, a P-type ATPase, are not driven by ATP-induced conformational changes.
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 A) 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.
Haupt
Melina
M
Institut für Organische Chemie und Biochemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany.
Bramkamp
Marc
M
Coles
Murray
M
Altendorf
Karlheinz
K
Kessler
Horst
H
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012996:Solutions
D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; D012996:Solutions; D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C058166:potassium translocating Kdp-ATPase, E coli