Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K+ and Na+ of the Na+ dependent K+ uptake system KtrAB from Vibrio alginolyticus

Autor(en): Tholema, N
Bakker, EP
Suzuki, A
Nakamura, T
Stichwörter: Biochemistry & Molecular Biology; Biophysics; Cell Biology; CHANNEL; ENCODES; ENTEROCOCCUS-HIRAE; ESCHERICHIA-COLI; GENE; HKT1; K+ symporter family; KcsA-K+ channel family; Na+/K+ symporter; P-loop; POTASSIUM-TRANSPORT; SACCHAROMYCES-CEREVISIAE; selectivity filter; SITE-DIRECTED MUTAGENESIS; SODIUM; TRK SYSTEM
Erscheinungsdatum: 1999
Volumen: 450
Ausgabe: 3
Startseite: 217
Seitenende: 220
KtrAB from Vibrio alginolyticus is a recently described new type of high affinity bacterial K+ uptake system. Its activity assayed in an Escherichia coli K+ uptake negative mutant depended on Na+ ions (K-m of 40 mu M). Subunit KtrB contains four putative P-loops, The selectivity filter from each P-loop contains a conserved glycine residue. Residue Gly-290 from the third P-loop selectivity filter in KtrB mas exchanged for Ala, Ser or Asp. KtrB variants Ser-290 and Asp-290 were without activity. In contrast, KtrB variant Ala-290 was still active. This variant transported K+ with a two orders of magnitude decrease in apparent affinity for both K+ and Na+ with little effect on V-max. (C) 1999 Federation of European Biochemical Societies.
ISSN: 00145793
DOI: 10.1016/S0014-5793(99)00504-9

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