tailieunhanh - Báo cáo khoa học: The KdpC subunit of the Escherichia coli K+-transporting KdpB P-type ATPase acts as a catalytic chaperone

In Bacteria and Archaea, high-affinity potassium uptake is mediated by the ATP-driven KdpFABC complex. On the basis of the biochemical properties of the ATP-hydrolyzing subunit KdpB, the transport complex is classified as type IA P-type ATPase. | IFEBS Journal The KdpC subunit of the Escherichia coli K -transporting KdpB P-type ATPase acts as a catalytic chaperone Kristina Irzik1 Juliane Pfrỏtzschner1 Tatjana Goss1 Franziska Ahnert1 Melina Haupt2 and Jorg-Christian Greie1 1 Fachbereich Biologie Chemie Universitat Osnabruck Germany 2 Institut Laue Langevin Deuteration Laboratory Grenoble France Keywords ABC transporter ion pump KdpFABC P-type ATPase potassium transport Correspondence . Greie Fachbereich Biologie Chemie Universitat Osnabruck BarbarastraBe 11 49069 Osnabruck Germany Fax 49 541 9692870 Tel 49 541 9692809 E-mail greie@ These authors contributed equally to this work Received 26 April 2011 revised 31 May 2011 accepted 24 June 2011 doi In Bacteria and Archaea high-affinity potassium uptake is mediated by the ATP-driven KdpFABC complex. On the basis of the biochemical properties of the ATP-hydrolyzing subunit KdpB the transport complex is classified as type IA P-type ATPase. However the KdpA subunit which promotes K transport clearly resembles a potassium channel such that the KdpFABC complex represents a chimera of ion pumps and ion channels. In the present study we demonstrate that the blending of these two groups of transporters in KdpFABC also entails a nucleotide-binding mechanism in which the KdpC subunit acts as a catalytic chaperone. This mechanism is found neither in P-type ATPases nor in ion channels although parallels are found in ABC transporters. In the latter the ATP nucleotide is coordinated by the LSGGQ signature motif via double hydrogen bonds at a conserved glutamine residue which is also present in KdpC. High-affinity nucleotide binding to the Kdp-FABC complex was dependent on the presence of this conserved glutamine residue in KdpC. In addition both ATP binding to KdpC and ATP hydrolysis activity of KdpFABC were sensitive to the accessibility presence or absence of the hydroxyl groups at the ribose moiety of the .