Showing papers by "Erhard Bremer published in 1995"
TL;DR: DNA sequence analysis revealed that the components of the OpuA system are encoded by an operon (opuA) comprising three structural genes: opuAA, opuAB, and opuAC, which exhibit features characteristic for binding protein-dependent transport systems and in particular show homology to the glycine betaine uptake system ProU from E. coli.
178 citations
TL;DR: It is demonstrated that the binding-protein-dependent ProU transport system of E. coli mediates the efficient uptake of the osmoprotectants glycine betaine and proline betaine.
Abstract: The ProP and ProU transport systems of Escherichia coli mediate the uptake of several osmoprotectants including glycine betaine. Here we report that both ProP and ProU are involved in the transport of the potent osmoprotectant proline betaine. A set of isogenic E. coli strains carrying deletions in either the proP or proU loci was constructed. The growth properties of these mutants in high osmolarity minimal media containing 1 mM proline betaine demonstrated that the osmoprotective effect of this compound was dependent on either an intact ProP or ProU uptake system. Proline betaine competes with glycine betaine for binding to the proU-encoded periplasmic substrate binding protein (ProX) and we estimate a KD of 5.2 μM for proline betaine binding. This value is similar to the binding constant of the ProX protein determined previously for the binding of glycine betaine (KD of 1.4 μM). Our results thus demonstrate that the binding-protein-dependent ProU transport system of E. coli mediates the efficient uptake of the osmoprotectants glycine betaine and proline betaine.
140 citations