KtrB, a member of the superfamily of K+ transporters
Autor(en): | Haenelt, Inga Tholema, Nancy Kroening, Nadine Vor der Brueggen, Marc Wunnicke, Dorith Bakker, Evert P. |
Stichwörter: | AMINO-ACID SUBSTITUTIONS; CATION-TRANSPORT; Cell Biology; CRYSTAL-STRUCTURE; ESCHERICHIA-COLI; HIGH-AFFINITY; HKT; K+ -selectivity filter; K+ channel KcsA; K+ transport; Kdp system; KDP-ATPASE; Kef system; KTN domain; MEMBRANE REGION M-2C2; POTASSIUM CHANNEL; RCK domain; SKT proteins; Trk system; UPTAKE SYSTEM KTRAB; VIBRIO-ALGINOLYTICUS | Erscheinungsdatum: | 2011 | Herausgeber: | ELSEVIER GMBH | Journal: | EUROPEAN JOURNAL OF CELL BIOLOGY | Volumen: | 90 | Ausgabe: | 9 | Startseite: | 696 | Seitenende: | 704 | Zusammenfassung: | KtrB is the K+-translocating subunit of the K+-uptake system KtrAB from bacteria. It is a member of the (s) under bar uperfamily of (K) under bar (+) (t) under bar ransporters (SKT proteins) with other sub-families occurring in archaea, bacteria, fungi, plants and trypanosomes. SKT proteins may have originated from small K+ channels by at least two gene duplication and two gene fusion events. They contain four covalently linked M1PM2 domains, in which M-1 and M-2 stand for transmembrane stretches, and P for a P-loop, which folds back from the external medium into the membrane. SKT proteins distinguish themselves in two important aspects from K+ channels: first, with just one conserved glycine residue in their P-loops they contain a much simpler K+-selectivity filter sequence than K+ channels with their conserved Thr-Val-Gly-Tyr-Gly sequence. Secondly, the middle part M-2C2 from the long transmembrane stretch M-2C of KtrB from the bacterium Vibrio alginolyticus forms a gate inside the membrane, which prevents K+ permeation to the cytoplasm. Beside the mechanism of K+ transport via KtrB and other SKT proteins existing hypotheses of how the KtrA protein regulates the K+-transport activity of KtrB are discussed. (C) 2011 Elsevier GmbH. All rights reserved. |
ISSN: | 01719335 | DOI: | 10.1016/j.ejcb.2011.04.010 |
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