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Phosphotransfer circuitry of the putative multi-signal transducer, ArcB, of Escherichia coli: in vitro studies with mutants (1995)

Tsuzuki, Masakatsu ; Ishige, Kazuya ; Mizuno, Takeshi

Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd

Molecular microbiology 18 (1995), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: Recently we demonstrated the occurrence of a novel device of signal transducers in Escherichia coli. This class of bacterial sensory kinases, typified by ArcB and BarA, possesses two phospho-donor (His) sites, together with a phospho-accepting (Asp) site. These multi-phosphorylation sites were suggested to make a phosphotransfer circuit. To clarify this complex circuitry, we carried out a series of in vitro assays involving a set of ArcB mutant proteins which have an amino acid substitution at each putative phosphorylation site (His-292, Asp-576 and His-717). By these in vitro phosphorylation and/or phosphotransfer assays, the followings were assessed: (i) ArcB autophosphorylation; (ii) ArcB-mediated phosphorylation of the cognate response regulator, ArcA; (iii) ArcB-mediated phosphorylation of its truncated form (ArcBc) encompassing only the C-terminal phosphorylation site (His-717); (iv) phosphotransfer from ArcBc to ArcA; and (v) phosphotransfer from ArcBc to ArcB. On the basis of these in vitro results, a complex circuitry was revealed for the signal transducer ArcB. This evidence obtained in vitro supports the view that ArcB can serve as a powerful device for not only propagating multi-signals, but also making up signalling networks, in ways more sophisticated than previously thought.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2958.1995.18050953.x

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Gene activation by theEscherichia coli positive regulator OmpR: A mutational study of the DNA-binding domain of OmpR (1995)

Kato, Naoki ; Tsuzuki, Masakatsu ; Aiba, Hirofumi ; [et al.]

Springer

Molecular genetics and genomics 248 (1995), S. 399-406

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ISSN: 1617-4623

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract TheEscherichia coli DNA-binding protein, OmpR, is one of the best characterized of the bacterial positive regulators that enhance the transcriptional ability of RNA polymerase. OmpR, consisting of 239 amino acids, binds to specific sequences located upstream of the cognateompC andompF promoters. The C-terminal half of OmpR, consisting of about 120 amino acids, exhibits an inherent DNA-binding ability. To address the issue of DNA binding by OmpR, we selected a set of OmpR mutants, each of which has a single amino acid substitution in the C-terminal half of OmpR. In particular, we characterized a number of OmpR mutants which are defective in DNA binding and thereby result in an OmpF− OmpC phenotype. Among them, a putative positive control OmpR mutant was also obtained, which appears to be defective in phosphorylation-dependent transcriptional activation, but not in DNA binding. These results are discussed with general emphasis on DNA recognition by theE. coli family of OmpR-like regulatory proteins.