response regulator proteins in bacteria
Molecular Mechanisms of Signal Transduction : "The majority of bacterial response regulator proteins are transcription factors that serve as repressors or activators to regulate the expression of specific genes. The effector domains of these response regulators are DNA-binding domains that can be categorized into three major families based on sequence and structural similarity.
The OmpR/PhoB family of response regulator transcription factors, distinguished by a winged-helix DNA-binding domain, is the largest family, accounting for ~45 percent of all response regulators. Most characterized members of this family have been shown to bind as tandem dimers to direct repeat DNA recognition sequences. . . Phosphorylation induces dimerization or higher-order oligomerization of the proteins and that dimerization is mediated by the phosphorylated regulatory domains. The activated regulatory domains of Escherichia coli ArcA, KdpE, PhoB, PhoP, and TorR and T. maritima DrrB and DrrD all exist as dimers with identical alpha4-beta5-alpha5 interfaces. In all cases, the dimerization interface is formed by a few hydrophobic residues surrounded by an extensive network of intra- and intermolecular salt bridges. The residues involved in these interactions are highly conserved in all members of the OmpR/PhoB family, but not in other response regulators. It is proposed that this mode of dimerization is common to most members of the OmpR/PhoB family and that it represents a family-specific mechanism for activation of DNA binding. Upon phosphorylation, the interface between regulatory and DNA-binding domains is disrupted, allowing the regulatory domains to dimerize via their alpha4-beta5-aalpha5 faces. Disruption of the interdomain interface frees the DNA-binding domain, allowing it to dimerize in tandem on direct repeat DNA half-sites with symmetry that is different from that of the regulatory domain dimer. Additional nuclear magnetic resonance (NMR) and biochemical studies support this mechanism of activation. " Link to link-to-images.
The OmpR/PhoB family of response regulator transcription factors, distinguished by a winged-helix DNA-binding domain, is the largest family, accounting for ~45 percent of all response regulators. Most characterized members of this family have been shown to bind as tandem dimers to direct repeat DNA recognition sequences. . . Phosphorylation induces dimerization or higher-order oligomerization of the proteins and that dimerization is mediated by the phosphorylated regulatory domains. The activated regulatory domains of Escherichia coli ArcA, KdpE, PhoB, PhoP, and TorR and T. maritima DrrB and DrrD all exist as dimers with identical alpha4-beta5-alpha5 interfaces. In all cases, the dimerization interface is formed by a few hydrophobic residues surrounded by an extensive network of intra- and intermolecular salt bridges. The residues involved in these interactions are highly conserved in all members of the OmpR/PhoB family, but not in other response regulators. It is proposed that this mode of dimerization is common to most members of the OmpR/PhoB family and that it represents a family-specific mechanism for activation of DNA binding. Upon phosphorylation, the interface between regulatory and DNA-binding domains is disrupted, allowing the regulatory domains to dimerize via their alpha4-beta5-aalpha5 faces. Disruption of the interdomain interface frees the DNA-binding domain, allowing it to dimerize in tandem on direct repeat DNA half-sites with symmetry that is different from that of the regulatory domain dimer. Additional nuclear magnetic resonance (NMR) and biochemical studies support this mechanism of activation. " Link to link-to-images.
posted at 12/13/2006 11:46:00 PM
