Team:Groningen/project degradation tags

Bacteria are able to synthesize a special RNA called SsrA RNA which is able to function both as tRNA and mRNA during the protein synthesis. This RNA fragment acts when there is an incomplete or untranslatable part in the RNA being translated. Translation stalls which ends up with SsrA (which has a charged alanine group that binds to the polypeptide chain leaving the ribosome) being recognized by the ribosome as a tRNA. SsrA binds to the ribosome and the message is changed to the tRNA part of SsrA which codes for a degradation tail, in our case an LVA tag. An LVA tag has an amino acid sequence of AANDENYALVA. In bacteria this tail acts as a precursor for fast degradation. Some chaperons found in the same bacteria, mainly ClpAP and ClpXP, recognizes this tail and degrades this wrongly translated polypeptide. This way the bacterium can get rid of the unwanted product which may even harm itself. In our project we did not use SsrA to add the degradation tag but we synthetically added the degradation tag to the DNA sequence of the proteins that are needed to be expressed for a short amount of time. With this ClpXP is able to recognize these proteins and degrade them in a short amount of time.

Mechanism in which the degradation tags function in the cell.
source:The SsrA–SmpB system for protein tagging, directed degradation and ribosome rescue. A. Wali Karzai, Eric D. Roche and Robert T. Sauer