Potassium uptake with low affinity and high rate in Enterococcus hirae at alkaline Ph

Citation
M. Kawano et al., Potassium uptake with low affinity and high rate in Enterococcus hirae at alkaline Ph, ARCH MICROB, 175(1), 2001, pp. 41-45
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ARCHIVES OF MICROBIOLOGY
ISSN journal
0302-8933 → ACNP
Volume
175
Issue
1
Year of publication
2001
Pages
41 - 45
Database
ISI
SICI code
0302-8933(200101)175:1<41:PUWLAA>2.0.ZU;2-Z
Abstract
Two high-affinity K+ uptake systems, KtrI and KtrII, have been reported in Enterococcus hirae. A mutant, JEMK1, defective in these two systems did not grow at pH 10 in low-K+ medium (less than 1 mM K+), but grew well when sup plemented with 10 mM KCl. In this mutant. we found an energy-dependent K+ u ptake at pH 10 with a low affinity for K+ (K-m of similar to 20 mM) and an extremely high rate [V-max of 1.6 mu mol min(-1) (mg protein)(-1)]. Rb+ upt ake [K-m of similar to 40 mM and V-max of 0.5 mu mol min(-1) (mg protein)(- 1), which was inhibited competitively by Ki and less prominently by Cs+, wa s also observed. The specificity of this transport is likely to be K+>Rb+>C s+. This peculiar K+ transport plays a role as a salvage mechanism against defects in high-affinity systems in the K+ homeostasis of this bacterium.