Argonaute proteins are present in many bacteria, but their role has long remained elusive.
In this thesis it is demonstrated that Argonaute proteins function as a bacterial immune-system, which protects the bacterial host against invaders such as viruses and plasmids. Argonaute proteins can do this by acquiring a small piece of DNA from the invader. After this, Argonaute can use this piece of DNA as a ‘guide’. when Argonaute finds another piece of DNA with a matching sequence, that DNA is bound and degraded. This neutralizes the invader.
Besides that this is interesting from a fundamental point of view, it is revealed that it is possible to program Argonaute proteins with synthetic DNA guides. This allows to program Argonaute proteins to cleave any desired DNA sequence, which is a useful tool for research purposes.