Characterization of the osmoregulated Escherichia coli proU promoter and identification of ProV as a membrane‐associated protein

Abstract

The Escherichia coli proU operon encodes a high-affinity, binding-protein-dependent transport system for the osmoprotectant glycine betaine. Expression of proU is osmoregulated, and transcription of this operon is greatly increased in cells grown at high osmolarity. Characterization of the proU operon and its promoter provided results similar to those published elsewhere (Gowrishankar, 1989; Stirling et al., 1989). The previously identified proU601 mutation, which leads to increased proU expression both at low- and high osmolarity, is a G to A transition in the Pribnow box of the proU promoter, which increases the homology of the -10 region to the consensus sequence of E. coli promoters. Using an antiserum raised against a ProV-beta-galactosidase hybrid protein, we have identified ProV as a protein associated with the cytoplasmic membrane. This cellular location is consistent with its proposed role as the energy-coupling component of the ProU transport system.

Characterization of mutations affecting the osmoregulated proU promoter of Escherichia coli and identification of 5' sequences required for high-level expression

“…We have previously reported that multicopy plasmids carrying the proU601 mutation in a FD(proV-lacZ)(Hyb2) fusion plasmid rapidly acquire secondary mutations that strongly decrease the expression of the fusion (31 (33). When these clones were sequenced, a variety of mutations in the proU promoter were recovered.…”

“…No classical regulatory protein has been identified for proU. Mutants with increased proU expression carry either cis-acting mutations closely linked to proU (12,23,31) or trans-acting mutations in topA or osmZ (23). The products of these genes, DNA topoisomerase I and the histonelike DNAbinding protein H-NS (Hla), respectively, are known to affect DNA topology, and mutations in these genes increase moters; however, the proU -10 region deviates from the consensus (TATAAT) sequence at three positions (22).…”

“…ProU is a binding-protein-dependent transport system and is encoded by the proU operon, which consists of three structural genes, proV, proW, and proX (20,31,41,52). The level of proU expression is sensitively determined by the osmolarity of the growth medium.…”

Different strategies of osmoadaptation in the closely related marine myxobacteria Enhygromyxa salina SWB007 and Plesiocystis pacifica SIR-1

“…coli can synthesize the compatible solute trehalose de novo and can convert choline to glycine betaine. If provided with the medium, E. coli is able to transport and amass a variety of different compatible solutes, such as ectoine, proline and glycine betaine, with the help of the transporters ProP and ProU (Milner et al, 1988;May et al, 1989). In order to feed myxobacteria without contaminating compatible solutes, we designed the trehalose-free E. coli strain BKA-13, which is based on E. coli MHK-13 (Haardt et al, 1995).…”

La réponse au stress osmotique des bactéries lactiques Lactococcus lactis et Lactobacillus plantarum (mini-revue)

“…Chez E. coli, l'ABC transporteur ProU est localisé au niveau de l'enveloppe et est composé de 3 protéines : une protéine cytoplasmique d'hydrolyse de l'ATP (ATPase ou ATPbinding cassette, ProV), caractéristique des ABC transporteurs, qui fournit l'énergie au système, une protéine membranaire (ou perméase, ProW) servant au passage de la glycine bétaïne vers le milieu interne et un polypeptide périplasmique hydrophile de liaison au substrat (ProX). La perméase ProW est constituée de 6 domaines transmembranaires aux extrémités carboxy-et amino-terminale cytoplasmiques et semble fonctionner comme un homodimère avec l'ATPase ProV [1,23]. Chez L. lactis, l'étude de la séquence de l'opéron opuA indique que ce système appartient à la superfamille des ABC transporteurs.…”