Journal of Bioenergetics and Biomembranes

, Volume 39, Issue 5, pp 397–402

The K+-translocating KdpFABC complex from Escherichia coli: A P-type ATPase with unique features

Transport ATPases: Structure, Mechanism and Relevance to Multiple Diseases

DOI: 10.1007/s10863-007-9111-0

Cite this article as:
Greie, JC. & Altendorf, K. J Bioenerg Biomembr (2007) 39: 397. doi:10.1007/s10863-007-9111-0

Abstract

The prokaryotic KdpFABC complex from the enterobacterium Escherichia coli represents a unique type of P-type ATPase composed of four different subunits, in which a catalytically active P-type ATPase has evolutionary recruited a potassium channel module in order to facilitate ATP-driven potassium transport into the bacterial cell against steep concentration gradients. This unusual composition entails special features with respect to other P-type ATPases, for example the spatial separation of the sites of ATP hydrolysis and substrate transport on two different polypeptides within this multisubunit enzyme complex, which, in turn, leads to an interesting coupling mechanism. As all other P-type ATPases, also the KdpFABC complex cycles between the so-called E1 and E2 states during catalysis, each of which comprises different structural properties together with different binding affinities for both ATP and the transport substrate. Distinct configurations of this transport cycle have recently been visualized in the working enzyme. All typical features of P-type ATPases are attributed to the KdpB subunit, which also comprises strong structural homologies to other P-type ATPase family members. However, the translocation of the transport substrate, potassium, is mediated by the KdpA subunit, which comprises structural as well as functional homologies to MPM-type potassium channels like KcsA from Streptomyces lividans. Subunit KdpC has long been thought to exhibit an FXYD protein-like function in the regulation of KdpFABC activity. However, our latest results are in favor of the notion that KdpC might act as a catalytical chaperone, which cooperatively interacts with the nucleotide to be hydrolyzed and, thus, increases the rather untypical weak nucleotide binding affinity of the KdpB nucleotide binding domain.

Keywords

KdpP-type ATPasePotassiumPotassium channelFRETALEX-FRET

Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  1. 1.Universität Osnabrück, Fachbereich Biologie/Chemie, Arbeitsgruppe MikrobiologieOsnabrückGermany