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

被引:77
作者
Tholema, N
Bakker, EP
Suzuki, A
Nakamura, T
机构
[1] Univ Osnabruck, Abt Mikrobiol, D-49069 Osnabruck, Germany
[2] Chiba Univ, Fac Pharmaceut Sci, Lab Membrane Biochem, Inage Ku, Chiba 263, Japan
关键词
K+ symporter family; Na+/K+ symporter; HKT1; P-loop; selectivity filter; KcsA-K+ channel family;
D O I
10.1016/S0014-5793(99)00504-9
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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.
引用
收藏
页码:217 / 220
页数:4
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