title: Cyclic AMP-dependent osmoregulation of crp gene expression in Escherichia coli.
abstract: We have found that the cyclic AMP (cAMP) receptor protein (CRP)-cAMP regulatory complex in Escherichia coli is subject to osmoregulation at the level of crp gene expression. This osmoregulation was lost in a cya mutant strain but could be restored by external addition of cAMP, suggesting that the intracellular level of cAMP is a key factor in the osmoregulation of CRP. The ability of the cell to maintain optimal CRP activity was essential for the growth and survival of the bacteria under low-osmolarity conditions as shown by studies with different crp mutant alleles. A suppressor mutant with a novel amino acid substitution (L124R) in CRP showed restored growth at low osmolarity. CRP(L124R) was not activated by cAMP and was shown to be dominant negative over the wild type. Our findings suggest that the fine-tuning of the CRP activity may be critical for bacterial viability and adaptability to changing osmotic conditions.
authors.affiliation: Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain. cbalsalobre@ub.edu
authors.forename: Carlos
authors.initials: C
authors.lastname: Balsalobre
authors.forename: Jörgen
authors.initials: J
authors.lastname: Johansson
authors.forename: Bernt Eric
authors.initials: BE
authors.lastname: Uhlin
mesh_terms: D000242:Cyclic AMP / Q000378:metabolism*; D002373:Cyclic AMP Receptor Protein; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; D011956:Receptors, Cell Surface; D014157:Transcription Factors; C481662:crp protein, E coli; D000242:Cyclic AMP