Template:Team:Bonn:NetworkData

content.i =40;

content.parents=[38];

content.childs=[41,42,43,44];

content.titleShort="universal application";

content.titleLong="universal applications";

content.summary="discussing the universal applications of the c.crescentus ClpXP degradation system";

content.text="";

content.type="Project"

content.i =41;

content.parents=[40];

content.childs=[];

content.titleShort="ClpXP";

content.titleLong="ClpXP";

content.summary="brief introduction to the ClpXP complex";

content.text="";

content.type="Project"

content.summary= "This article deals with the Structure of sspBα and conformational details of its binding to ssrA and ClpXP during tethering.";

content.text= "<div class='content-image'><img src='https://static.igem.org/mediawiki/2013/thumb/4/42/Bonn_OutlookCCSspB1_Version2.png/726px-Bonn_OutlookCCSspB1_Version2.png'>sspB structure and its conservation among C. crescentus, E. coli and H. influenzae [42.1]</div>The sspB&alpha; dimeric structure is stabilized by two &alpha;-helices in interaction, as part B of the figure above shows, each of them located at the N-terminus of either sspB&alpha; molecule. The subsequent parts of the protein form a domain consisting of two &beta;-sheet structures, together building up the ssrA binding site. An unstructured area at the C-terminus being referred to as the XB module forms the ClpX binding part of the protein. It is connected to the rest of the molecule via a linker domain. [42.2]Chien et al. [42.1] compared crystal structures of C. crescentus sspB&alpha; and its E. coli and H. influenzae sspB orthologs, discovering that in sspB&alpha; the &alpha;-helices are significantly longer, more twisted and cover a larger cross section area than the other two sspB orthologs. Also considering that &beta;-sheets are rotated by around 20&deg; in comparison to E. coli and H. influenzae orthologs, this leads to an antiparallel orientation of the two ssrA tagged protein bound to the ssrA binding sites of an sspB&alpha; dimer in C. crescentus, while they are parallel in &gamma;-protobacterial sspB. </br></br> <div class='content-image'><img src='https://static.igem.org/mediawiki/2013/6/6c/Bonn_OutlookCCSspB2.png' align=left>By measuring GFP fluorescence intensity, decrease of GFP-^CCssrA concentration (1) without sspB&alpha; added, (2) with mutated sspB&alpha;(Q74A) added , (3) with wildtype sspB&alpha; added can be visualized. [42.1]</div> Chien et al. point out that although there are the remarkable differences in protein structure between sspB&alpha; and its &gamma;-protobacterial ortholog, they show up with similar effectiveness in binding proteins tagged with the related ssrA peptide. But it turned out in their research that effectiveness of sspB&alpha; binding to the protein which needs to be tethered to the ClpXP protease strongly depends on which ssrA ortholog the protein is tagged with. sspB&alpha; binds firmly to ^CCssrA, with an affinity being 175 times as large as for binding to ^ECssrA (i.e. the E. coli ortholog). By comparing the crystal structures of both sspB&alpha; and the compound of sspB&alpha; and ^CCssrA, Chien et al. further proved that binding of sspB&alpha; to ^CCssrA does not lead to significant changes of its 3D conformation. </br></br> <h2>References</h2> </br>[42.1] Structure and substrate specificity of an SspB ortholog: design implications for AAA+ adaptors, Chien et al., Cell Press, 2007, PMID: 17937918 </br> [42.2] Bivalent tethering of sspB to ClpXP is required for efficient substrate delivery: a protein design study, Bolon DN et al., Mol Cell, 2004, PMID: 14967151"; <!-- References-Ueberschrift muss an Format des Bildes angepasst werden -->

content.titleLong = "C. crescentus ssrA";

content.text= "";  

content.text= "ssrA and sspB are peptides that mediate proteolysis via the ClpXP protease system in bacteria. In this article and the related articles, focus is laid on their orthologs in C. crescentus, being referred to as ^CCssrA and <sup>CC>/sup>sspB&alpha;, respectively, omitting <b>????????????????</b> when obvious out of context. The ClpXP protease has an important function in regulation of the cell division cycle by effective proteolysis of short-lived regulatory proteins. A protein which needs to be degraded will be tagged with the amino acid peptide ^CCssrA, which is added at its C-terminus during translation. [74.1, 74.2] The ClpX subunit of the ClpXP protease recognizes the ssrA tag by specific binding and unfolds the tagged protein, in which ATP is hydrolyzed. In C. crescentus, the ssrA tag has a length of 14 amino acids, while the E. coli ortholog is only eleven amino acids long. sspB&alpha; is a dimeric protein that serves as a tether which brings the ssrA-tagged protein and the ClpXP protease together and therefore accelerates protein degradation. It simultaneously binds to both the ssrA tag and the ClpX subunit and in this way brings the tagged protein in close contact with the protease. </br></br> <h2>References</h2> </br> [74.1] Overlapping recognition determinants within the ssrA degradation tag allow modulation of proteolysis, Flynn et al., Proceedings of the National Academy of Sciences of the United States of America, 2001, PMID: 11535833 </br> [74.2] Structure and substrate specificity of an SspB ortholog: design implications for AAA+ adaptors, Chien et al., Cell Press, 2007, PMID: 17937918";