Open AccessOsmotic regulation of transcription: induction of the proU betaine transport gene is dependent on accumulation of intracellular potassium
Author(s) -
Lesley Sutherland,
John Cairney,
M Elmore,
Ian R. Booth,
Christopher F. Higgins
Publication year - 1986
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.168.2.805-814.1986
Subject(s) - betaine , osmoprotectant , biology , operon , potassium , turgor pressure , biochemistry , osmotic concentration , osmotic shock , intracellular , microbiology and biotechnology , proline , biophysics , mutant , gene , chemistry , amino acid , organic chemistry
The proU locus, which encodes a high-affinity betaine transport system, and the kdp operon, which encodes a potassium transport system, are the principal osmoresponsive genes in Escherichia coli and Salmonella typhimurium. The kdp operon is known to be induced in response to changes in cell turgor. We have investigated the control of proU expression and shown that it differs from that of kdp in a number of fundamental ways. Rather than responding to changes in turgor, proU expression is principally determined by the intracellular accumulation of potassium ions. Potassium and betaine were shown to play distinct osmoprotective roles. Potassium serves as the principal osmoprotectant and is accumulated in response to low-level osmotic stress to restore turgor. As external osmolarity is increased to a level at which the corresponding increase in internal potassium concentrations is potentially deleterious to enzyme function, betaine (when available) is accumulated in preference to potassium. The different mechanisms of proU and kdp regulation reflect the different physiological roles of these two osmoprotectants.