Sandbox Reserved 344: Difference between revisions
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=Introduction= | =Introduction= | ||
PhoP is a cytoplasmic response regulator from the two component system PhoP/PhoQ. This system responds mainly to changes in extracellular Mg<sup>2+</sup> concentration and is an important part of the signal pathway leading to a coordinated cell response in gram-negative bacteria such as ''Escherichia coli'' and ''Salmonella enterica''. PhoQ, located across the inner membrane, responds to low Mg<sup>2+</sup> concentration by phosphorylating PhoP. Phosphorylated PhoP forms a homodimer and affects gene expression and other two component systems. Gene regulation is achieved by the increased affinity of the homodimer to the PhoP box, a tandem repeat promoter. The response is organism specific but generally involves survival in low Mg2+ environments and virulence. <ref name = "Bachh2007"> PMID:17545283</ref> | PhoP is a cytoplasmic response regulator from the two component system PhoP/PhoQ. This system responds mainly to changes in extracellular Mg<sup>2+</sup> concentration and is an important part of the signal pathway leading to a coordinated cell response in gram-negative bacteria such as ''Escherichia coli'' and ''Salmonella enterica''. PhoQ, located across the inner membrane, responds to low Mg<sup>2+</sup> concentration by phosphorylating PhoP. Phosphorylated PhoP forms a homodimer and affects gene expression and other two component systems. Gene regulation is achieved by the increased affinity of the homodimer to the PhoP box, a tandem repeat promoter. The response is organism specific but generally involves survival in low Mg2+ environments and virulence. <ref name = "Bachh2007"> PMID:17545283</ref><ref name = "Groisman"> PMID:11222580</ref> | ||
=Structure= | =Structure= | ||
PhoP consists of 2 domains, the regulatory domain and the C-terminal effector domain. | PhoP consists of 2 domains, the regulatory domain and the C-terminal effector domain. | ||
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Two component systems allow bacteria to respond to changes in their environment. These systems are found mainly in prokaryotes and a few eukaryotes (mack). 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. (Groisman) | Two component systems allow bacteria to respond to changes in their environment. These systems are found mainly in prokaryotes and a few eukaryotes (mack). 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. (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. | ||
The PhoP/PhoQ system may also be found in non-cytoplasmic pathogens, such as ''Erwinia carotovora supsb. carotovora'', a plant pathogen living in the intercellular fluid, or non-pathogenic bacteria <ref name = "Groisman" | The PhoP/PhoQ system may also be found in non-cytoplasmic pathogens, such as ''Erwinia carotovora supsb. carotovora'', a plant pathogen living in the intercellular fluid, or non-pathogenic bacteria <ref name = "Groisman"/> | ||
=Importance of PhoP= | =Importance of PhoP= | ||
PhoP/PhoQ plays in key role in certain bacteria becoming virulent. This makes it a promising target for vaccine and antimicrobial drug development. | PhoP/PhoQ plays in key role in certain bacteria becoming virulent. This makes it a promising target for vaccine and antimicrobial drug development. | ||
=References= | =References= | ||
<references/> | <references/> | ||