Team:UCLouvain/OurProject/ComRS Overview
Still with the aim of creating a rapid UV-response system, we elaborated a second approach based on a regulation pathway, the ComR and ComS system, originally found in Streptococcus thermophilius. Our goal is to produce a UV inducible promoter.
ComR and ComS mechanism
The ComR and ComS system controls natural competence and allows quorum sensing in S. thermophilius. In molecular biology, natural competence is a genetically specified ability of a bacteria to integrate “naked” extracellular DNA from its environment under natural conditions (no pre-treated cells). This specific feature observed by some bacteria is an interesting and convenient tool in bioengineering because it allows to modify the host genome without needing to perform any transformation.
The quorum sensing (QS) is a set of regulatory mechanisms of synchronization of the expression of particular genes within a bacterial population and according to its local density. ComS is a small peptide encoded in the genome. After synthesis, it is matured and extruded from the cell into the medium. The peptide’s import allows other cells to sense the signal. When a threshold level is reached it will trigger the competent state in the whole population. Indeed, once reimported in the cell ComS will be able to bind the ComR protein. This will allow the formation of a ternary complex (peptide-protein-DNA) with a specific DNA motif (ComR-box) and trigger the downstream gene’s expression (See schema here below).
ComS mature sequence is LPYFAGCL. An aromatic substitution by an alanine would block the binding to ComR. Hence our objective is to synthetize this peptide while replacing the tyrosine by an ortho-nitrobenzyl tyrosine (ONB-Tyr). This should indeed prevent the binding unless there is some UV exposure and the ONB, or photocage, is released. This will result in the induction by exposure of the gene expression controlled by the ComR box. Using a red fluorescence protein should signal the UV exposure.
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