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 | Herausgeber: | ELSEVIER SCIENCE BV | Journal: | FEBS LETTERS | Volumen: | 450 | Ausgabe: | 3 | Startseite: | 217 | Seitenende: | 220 | Zusammenfassung: | 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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geprüft am 19.05.2024