Difference between revisions of "Part:BBa K200000"

(RcsB and the positive feedback loop)
(RcsB and the positive feedback loop)
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It is important to note that RcsB is a global regulator found in many [http://en.wikipedia.org/wiki/Enterobacteria Enterobacteria]. In Salmonella, up to 38 genes were found to be up-regulated by RcsB including ftsZ which affects the rate of cell division. <cite>1</cite> The majority of upregulated genes are associated with enhancing structural integrety and acid resistance. 22 genes were found to be downregualted by RcsB in the same microarray experiment.<cite>3</cite>
 
It is important to note that RcsB is a global regulator found in many [http://en.wikipedia.org/wiki/Enterobacteria Enterobacteria]. In Salmonella, up to 38 genes were found to be up-regulated by RcsB including ftsZ which affects the rate of cell division. <cite>1</cite> The majority of upregulated genes are associated with enhancing structural integrety and acid resistance. 22 genes were found to be downregualted by RcsB in the same microarray experiment.<cite>3</cite>
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===<b>Colanic Acid Biosynthesis:</b>===
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The overexpression of RcsB is akin to fitting a stethoscope to the end of a megaphone. In essence, the sensitivity of the RCS Phosphorelay system becomes such that the smallest of membrane perturbations becomes sufficient to trigger colanic acid production. Thus, the background noise switches the RCS Phosphorelay system on permanently.
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There are a total of 19 genes involved in colonic acid biosynthesis, the best characterised of which are shown below.
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<html>
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</p><p class="ecoparagraph">
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<map name="MAP79413">
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<area coords="0,55,32,72" onmouseover="return overlib('RcsAB transcriptional dual regulator activates transcription from associated promoter<br><b>Distance to transcription start site:</b> -105.5 (ranging from -99 to -112)<br>
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<b>Evidence:</b> Binding of purified proteins [Wehland00], Site mutation [Wehland00]');" onmouseout="return nd();">
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<area coords="32,55,64,72" onmouseover="return overlib('RcsAB transcriptional dual regulator activates transcription from associated promoter<br><b>Distance to transcription start site:</b> -78.5 (ranging from -72 to -85)<br>
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<b>Evidence:</b> Gene expression analysis [Ebel99], Automated inference based on similarity to consensus sequences [Ebel99]');" onmouseout="return nd();">
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<area coords="274,41,338,72" onmouseover="return overlib(' <b>Gene:</b>  wzb    G7106    b2061    ECK2055<br><b>Location:</b> 2,133,679 <- 2,134,122  <br> <b>Product:</b> tyrosine phosphatase');" onmouseout="return nd();">
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<area coords="745,41,816,72" onmouseover="return overlib(' <b>Gene:</b>  wcaB    G7103    b2058    ECK2052<br><b>Location:</b> 2,130,091 <- 2,130,579  <br> <b>Product:</b> predicted colanic acid biosynthesis acyl transferase');" onmouseout="return nd();">
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<area coords="631,41,745,72"  onmouseover="return overlib(' <b>Gene:</b>  wcaA    G7104    b2059    ECK2053<br><b>Location:</b> 2,130,582 <- 2,131,421  <br> <b>Product:</b> predicted colanic acid biosynthesis glycosyl transferase');" onmouseout="return nd();">
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<area coords="122,41,274,72" onmouseover="return overlib(' <b>Gene:</b>  wza    G7107    b2062    ECK2056<br><b>Location:</b> 2,134,128 <- 2,135,267  <br> <b>Product:</b> lipoprotein required for capsular polysaccharide translocation through the outer membrane, subunit of capsular polysaccharide export apparatus');" onmouseout="return nd();">
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<area coords="338,41,619,72"  onmouseover="return overlib(' <b>Gene:</b>  wzc    G7105    b2060    ECK2054<br><b>Location:</b> 2,131,514 <- 2,133,676  <br> <b>Product:</b> tyrosine kinase involved in colanic acid biosynthesis, subunit of capsular polysaccharide export apparatus');" onmouseout="return nd();">
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<area coords="16,0,135,89"  onmouseover="return overlib('<b>Operon:</b> wzap (Experim. ev.)  <BR><b>Tr.Activators:</b> (RcsAB)');" onmouseout="return nd();">
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<area coords="0,0,818,89" onmouseover="return overlib('<b>Operon</b>: wza-wzb-wzc-wcaAB<br><b>Synonyms:</b> OP00290, cps, cpsB, cpsGB');" onmouseout="return nd();">
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</map>
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<img src="https://static.igem.org/mediawiki/2009/8/89/Op1.gif" usemap="#MAP79413" border="0">
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</html>
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===RcsB and the positive feedback loop===
 
===RcsB and the positive feedback loop===

Revision as of 09:58, 20 October 2009

Colanic acid global regulator -> RcsB

Regulation for Capsular Synthesis (RCS) Phosphorelay System

RcsB is a transcription factor that forms part of a phosphorelay system. As the name suggests, a phosphorelay system consists of a series of nodes down which a phosphate group is passed. The transfer of this phosphate group down along the Rcs relay system is initiated by membrane stress. Once the phosphate group has been passed to RcsB, it can bind to DNA and act as a transcription factor.

PhosRelay.png

The Rcs phosphorelay is composed of two membrane-anchored proteins, RcsC and RcsD, and a cytoplasmic protein, RcsB. In response to a signal, the sensor kinase RcsC autophosphorylates and the phosphoryl group is transferred to RcsB, via RcsD. RcsB can both homodimerise and heterodimerise with RcsA, these two complexes serve to regulate different operons.

RcsB as a transcription factor

Together, the RcsB~P homodimer and the RcsB~P+RcsA heterodimer are thought to regulate ~5% of the E.coli genome 4. RcsB~P acts as a positive regulator of a number of genes including capsule genes responsible for colanic acid production. 2 This is via the activation of the ugd/cps operon which is required for capsule synthesis.
Colanic acid is a heteropolymer containing glucose, galactose, fucose, and glucuronic acid.

It is important to note that RcsB is a global regulator found in many [http://en.wikipedia.org/wiki/Enterobacteria Enterobacteria]. In Salmonella, up to 38 genes were found to be up-regulated by RcsB including ftsZ which affects the rate of cell division. 1 The majority of upregulated genes are associated with enhancing structural integrety and acid resistance. 22 genes were found to be downregualted by RcsB in the same microarray experiment.3

Colanic Acid Biosynthesis:

The overexpression of RcsB is akin to fitting a stethoscope to the end of a megaphone. In essence, the sensitivity of the RCS Phosphorelay system becomes such that the smallest of membrane perturbations becomes sufficient to trigger colanic acid production. Thus, the background noise switches the RCS Phosphorelay system on permanently.

There are a total of 19 genes involved in colonic acid biosynthesis, the best characterised of which are shown below.


RcsB and the positive feedback loop

RcsB~P is able to heterodimerise with the protein RcsA. The RcsB~P+RcsA complex acts as a transcription factor that induces the expression of a number of genes. One of these genes codes for RcsA, this initiates a positive feedback loop.

Usage and Biology

 Colanic acid is an exopolysaccharide secreted by some bacterial species to protect themselves from the environment that surrounds them.

The gene was used alongside YgiV and Rfal by the Imperial iGEM 2009 [http://2009.igem.org/Team:Imperial_College_London The E.ncapsulator] team to upregulate colanic acid production as part of the auto-encapsulation mechanism.

Sequence and Features


Assembly Compatibility:
  • 10
    COMPATIBLE WITH RFC[10]
  • 12
    COMPATIBLE WITH RFC[12]
  • 21
    COMPATIBLE WITH RFC[21]
  • 23
    COMPATIBLE WITH RFC[23]
  • 25
    COMPATIBLE WITH RFC[25]
  • 1000
    COMPATIBLE WITH RFC[1000]


References

<biblio>

  1. 1 pmid=1597415
  2. 2 pmid=2404948
  3. 3 pmid=19124574

</biblio>