Team:UCLouvain/Approach2
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. 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 basal level is reached it will trigger a competence in the whole population. Indeed, once reimported in the cell the ComS will be able to bind 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).
Our little trick
The ComS’s mature sequence is LPYFAGCL. An aromatic’s substitution by an alanine would block the binding to ComR. Hence our objective is to synthetize this peptide while replacing the tyrosine by a tyrosine-ortho-nitro benzyl (tyr-ONB). This should indeed prevent the binding unless there is some UV exposure and the ONB or photocage is released. This will result in the gene’s expression controlled by the ComR box’s induced by exposure. Using a red fluorescence protein should signal the UV exposure.
