An active-like structure in the unphosphorylated StyR response regulator suggests a phosphorylation-dependent allosteric activation mechanism

Mario Milani, Livia Leoni, Giordano Rampioni, Elisabetta Zennaro, Paolo Ascenzi, Martino Bolognesi

Research output: Contribution to journalArticlepeer-review

Abstract

StyR belongs to the FixJ subfamily of signal transduction response regulators; it controls transcription of the styABCD operon coding for styrene catabolism in Pseudomonas fluorescens ST. The crystal structure of unphosphorylated StyR is reported at 2.2 Å resolution. StyR is composed of an N-terminal regulatory domain (StyR-N) and a C-terminal DNA binding domain (StyR-C). The two domains are separated by an elongated linker α helix (34 residues), a new feature in known response regulator structures. StyR-C is structured similarly to the DNA binding domain of the response regulator NarL. StyR-N shows structural reorganization of the phosphate receiving region involved in activation/homodimerization: specific residues adopt an "active-like" conformation, and the α4 helix, involved in dimerization of the homologous FixJ response regulator, is trimmed to just one helical turn. Overall, structural considerations suggest that phosphorylation may act as an allosteric switch, shifting a preexisting StyR equilibrium toward the active, dimeric, DNA binding form.

Original languageEnglish
Pages (from-to)1289-1297
Number of pages9
JournalStructure
Volume13
Issue number9
DOIs
Publication statusPublished - Sep 2005

ASJC Scopus subject areas

  • Molecular Biology
  • Structural Biology

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