title: Interactions between phage-shock proteins in Escherichia coli.
abstract: Expression of the pspABCDE operon of Escherichia coli is induced upon infection by filamentous phage and by many other stress conditions, including defects in protein export. Expression of the operon requires the alternative sigma factor sigma54 and the transcriptional activator PspF. In addition, PspA plays a negative regulatory role, and the integral-membrane proteins PspB and PspC play a positive one. In this study, we investigated whether the suggested protein-protein interactions implicated in this complex regulatory network can indeed be demonstrated. Antisera were raised against PspB, PspC, and PspD, which revealed, in Western blotting experiments, that PspC forms stable sodium dodecyl sulfate-resistant dimers and that the hypothetical pspD gene is indeed expressed in vivo. Fractionation experiments showed that PspD localizes as a peripherally bound inner membrane protein. Cross-linking studies with intact cells revealed specific interactions of PspA with PspB and PspC, but not with PspD. Furthermore, affinity-chromatography suggested that PspB could bind PspA only in the presence of PspC. These data indicate that regulation of the psp operon is mediated via protein-protein interactions.
authors.affiliation: Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Adams
authors.forename: Wieke
authors.initials: W
authors.lastname: Teertstra
authors.forename: Jeroen
authors.initials: J
authors.lastname: Demmers
authors.forename: Rolf
authors.initials: R
authors.lastname: Boesten
authors.forename: Jan
authors.initials: J
authors.lastname: Tommassen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003432:Cross-Linking Reagents; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C069816:phage shock protein, Bacteria; D005982:Glutathione Transferase