Sandbox Reserved 344: Difference between revisions
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The effector domain is activated when PhoP is in dimer form. There is no direct change in conformation conferred on the effector domain by the regulatory domain. The PhoP has a winged helix-turn-helix motif characteristic of the OmpR/PhoB family of response regulators. This winged helix-turn-helix allows binding to DNA and regulation of transcription. Binding occurs at promoters with two repeats of the sequence (T/G)GTTTA, known as the PhoP box.<ref name = "Groisman"/> | The effector domain is activated when PhoP is in dimer form. There is no direct change in conformation conferred on the effector domain by the regulatory domain. The PhoP has a winged helix-turn-helix motif characteristic of the OmpR/PhoB family of response regulators. This winged helix-turn-helix allows binding to DNA and regulation of transcription. Binding occurs at promoters with two repeats of the sequence (T/G)GTTTA, known as the PhoP box.<ref name = "Groisman"/> | ||
=Function= | =Function= | ||
Two component systems allow bacteria to respond to changes in their environment. These systems are found mainly in prokaryotes and a few eukaryotes | Two component systems allow bacteria to respond to changes in their environment. These systems are found mainly in prokaryotes and a few eukaryotes.<ref name = "Mack"> PMID:19371748</ref> The PhoP/PhoQ system, found specifically in gram-negative bacteria, react mainly to a drop in extracellular Mg<sup>2+</sup>. Since the magnesium concentration is typically lower inside the host cell compared to outside, this acts as a trigger to become virulent. Other functions activated by the PhoP/PhoQ system includes adaptation to low Mg<sup>2+</sup> conditions, changes in cell wall, expression of proteases to protect against antimicrobial peptides and various other species specific responses. PhoP in ''Salmonella enterica'' regulates up to 40 proteins.<ref name = "Groisman"/> | ||
PhoP is not limited to direct regulation of gene expression. PhoP may regulate other two component systems at transcription, posttranscription and posttranslation too, in fact PhoP activates the expression of its own phoP gene, resulting in positive feedback and definite conversion to virulence. | PhoP is not limited to direct regulation of gene expression. PhoP may regulate other two component systems at transcription, posttranscription and posttranslation too, in fact PhoP activates the expression of its own phoP gene, resulting in positive feedback and definite conversion to virulence. | ||
Further evidence to PhoP's role in response to the extracellular environment is given by evidence of sRNA regulation of the expression of the phoP gene. Envelope stress, though σ<sup>E</sup> and the sRNA MicA affects expression of the PhoPQ system. <ref name = "Coornaert"> PMID:20345657</ref> | Further evidence to PhoP's role in response to the extracellular environment is given by evidence of sRNA regulation of the expression of the phoP gene. Envelope stress, though σ<sup>E</sup> and the sRNA MicA affects expression of the PhoPQ system. <ref name = "Coornaert"> PMID:20345657</ref> | ||