Premium
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
Author(s) -
Tholema Nancy,
Bakker Evert P.,
Suzuki Ayako,
Nakamura Tatsunosuke
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00504-9
Subject(s) - chemistry , affinities , selectivity , alanine , stereochemistry , escherichia coli , protein subunit , amino acid , biochemistry , gene , catalysis
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 μM). 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 was 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 .