The abortive infection K (AbiK) system of Lactococcus lactis is a powerful antiviral defense mechanism that acts in the period after phage DNA enters the cell but before new progeny are released. The N-terminal domain of AbiK encodes a novel DNA polymerase that in vitro uses an internal amino acid to synthesize an un-templated DNA. The C-terminal domain of AbiK, on the other hand, has not been biochemically characterized. In the first of two projects presented in this thesis, strategies were

more »

... ised to identify the amino acid priming site in AbiK. A close examination of data has narrowed down the priming site to two highly-conserved tyrosines in the N-terminal sequence of AbiK. In the second project, the characterization of the AbiK's C terminal domain was undertaken to identify its function. This study uncovers a novel RNA modification activity, and provides evidence that AbiK's C-terminal domain has ribonuclease activity.