title: Self-cleavage of the Pseudomonas aeruginosa Cell-surface Signaling Anti-sigma Factor FoxR Occurs through an N-O Acyl Rearrangement.
abstract: The Fox system of Pseudomonas aeruginosa is a cell-surface signaling (CSS) pathway employed by the bacterium to sense and respond to the presence of the heterologous siderophore ferrioxamine in the environment. This regulatory pathway controls the transcription of the foxA ferrioxamine receptor gene through the extracytoplasmic function sigma factor σ(FoxI). In the absence of ferrioxamine, the activity of σ(FoxI) is inhibited by the transmembrane anti-sigma factor FoxR. Upon binding of ferrioxamine by the FoxA receptor, FoxR is processed by a complex proteolytic cascade leading to the release and activation of σ(FoxI). Interestingly, we have recently shown that FoxR undergoes self-cleavage between the periplasmic Gly-191 and Thr-192 residues independent of the perception of ferrioxamine. This autoproteolytic event, which is widespread among CSS anti-sigma factors, produces two distinct domains that interact and function together to transduce the presence of the signal. In this work, we provide evidence that the self-cleavage of FoxR is not an enzyme-dependent process but is induced by an N-O acyl rearrangement. Mutation analysis showed that the nucleophilic side chain of the Thr-192 residue at +1 of the cleavage site is required for an attack on the preceding Gly-191, after which the resulting ester bond is likely hydrolyzed. Because the cleavage site is well preserved and the hydrolysis of periplasmic CSS anti-sigma factors is widely observed, we hypothesize that cleavage via an N-O acyl rearrangement is a conserved feature of these proteins.
authors: From the Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada E-18008, Spain and Section of Molecular Microbiology, Department of Molecular Cell Biology and.
authors: Karlijn C
authors: KC
authors: Bastiaansen
authors: Section of Molecular Microbiology, Department of Molecular Cell Biology and.
authors: Peter
authors: P
authors: van Ulsen
authors: Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands.
authors: Maikel
authors: M
authors: Wijtmans
authors: Section of Molecular Microbiology, Department of Molecular Cell Biology and.
authors: Wilbert
authors: W
authors: Bitter
authors: From the Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada E-18008, Spain and marian.llamas@eez.csic.es.
authors: María A
authors: http://orcid.org/0000-0002-9499-0492
authors: MA
authors: Llamas
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D020134:Catalytic Domain; D002462:Cell Membrane / Q000378:metabolism*; D004252:DNA Mutational Analysis; D003676:Deferoxamine / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D005290:Ferric Compounds / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D005998:Glycine / Q000737:chemistry; D006868:Hydrolysis; D019897:Periplasm / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017262:Siderophores / Q000737:chemistry*; D012808:Sigma Factor / Q000378:metabolism*; D015398:Signal Transduction; D013912:Threonine / Q000737:chemistry
chemical_list: D001425:Bacterial Outer Membrane Proteins; D005290:Ferric Compounds; D011956:Receptors, Cell Surface; D017262:Siderophores; D012808:Sigma Factor; C072460:foxR protein, bacteria; D013912:Threonine; C002577:ferrioxamine B; D003676:Deferoxamine; D005998:Glycine
keywords: Cell Signaling; Gene Regulation; Iron; Post-translational Modification (PTM); Proteolysis; Pseudomonas aeruginosa (P. aeruginosa); Siderophore; Signal Transduction