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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