Binding protein dependent transport of glycine betaine and its osmotic regulation in Escherichia coli K12

Abstract

Glycine betaine, which functions as an osmoprotectant, is accumulated to high intracellular concentrations in Escherichia coli at high osmolarity. We demonstrate the presence of a high-affinity, binding protein dependent transport system for glycine betaine, which is encoded by the proU region. We show the osmotically regulated synthesis of a 32 kDa periplasmic protein that is a glycine betaine binding protein with a KD of 1.4 microM. ProU-mediated glycine betaine transport is osmotically stimulated at the level of gene expression. The osmolarity of the medium also regulates the activity of the transport system, while binding of glycine betaine to its binding protein is independent of the osmolarity. We also find a second glycine betaine transport system that is dependent on proP and exhibits a lower substrate affinity. Like ProU, this system is regulated at two levels: both gene expression and the activity of the transport system are osmotically stimulated. Using lambda plac Mu-generated lacZ operon and gene fusions, we find that expression of the proU region is osmotically regulated at the level of transcription. We cloned a part of the proU region together with the phi(proU-lacZ)hyb2 gene fusion into a multicopy plasmid and show that the DNA sequences required in cis for osmotic regulation are present on the plasmid.

Identification of a central regulator of stationary‐phase gene expression in Escherichia coli

“…Relevant genotype F-, (argF-lac) UI69,araOl39,rpsL 150,ptsF25,flbB5301,rbsR,deoC,relAl MC4100, Silhavy et al (1984) G. May et al (1986) G. May et al (1986) G. May et al (1986) …”

Transport of glycine betaine in the extremely haloalkaliphilic sulphur bacterium Ectothiorhodospira halochloris

“…It will also be of interest to examine the properties of the transport protein and the molecular regulation of its expression. Detailed studies in E. coli (May et al, 1986;Barron et al, 1987) and in S . typhimuriurn (Cairney et al, 1985a, b ;Sutherland et al, 1986;Higgins et al, 1987) proved the existence of a low-affinity system, Prop, and a high-affinity transport system, ProU, which is induced by high osmolarities.…”

“…typhimuriurn (Cairney et al, 1985a, b ;Sutherland et al, 1986;Higgins et al, 1987) proved the existence of a low-affinity system, Prop, and a high-affinity transport system, ProU, which is induced by high osmolarities. The proU gene of these bacteria encodes a periplasmic betaine binding protein with a molecular mass of about 32kDa (May et al, 1986;Cairney et al, 1985~). Only recently, a periplasmic binding protein was identified in R .…”

“…In R. meliloti (Le Ruddier et al, 1991), A . brasilense sp7 and E. coli (May et al, 1986) Ectothiorhodospira halochloris, an extremely haloalkalip hilic p hototrop hic sulphur bacterium, uses glycine betaine as its main compatible solute in addition to ectoine and trehalose (Galinski & Truper, 1982). Glycine betaine cannot be used as carbon, nitrogen or energy source, and it cannot be stored as reserve material.…”

Importance of the High-Expression of Proline Transporter PutP to the Adaptation of <i>Escherichia coli</i> to High Salinity

“…To transport compatible solutes of proline in E. coli cells, three independent proline transporters, PutP, ProP and ProU, have been reported Wood, 1988;Bremer and Krämer, 2000 . The ProP and the ProU transporters operate for the accumulation of proline to high levels, which makes it possible for the cells to adapt to high salinity May et al, 1986 . The PutP transporter is required for the transport of proline when it is used as a carbon or nitrogen source Grothe et al, 1986 .…”