The role of antirestriction "DNA mimic" proteins in horizontal gene transfer and the spread of antibiotic resistance. (360G-Wellcome-080463_B_06_Z)

We propose to carry out a comprehensive genetic, biochemical and structural characterisation of the ardA and ardB antirestriction genes present on many mobile genetic elements residing in bacterial chromosomes as transposons and prophage. We wish to determine whether these Ard proteins are responsible for the extremely effective spread of antibiotic resistance genes also present on these mobile elements. The phenomenon of antirestriction may allow mobile elements to spread throughout bacterial populations despite the fact that the majority of bacteria have multiple and efficient restriction systems which, in the laboratory at least, represent a strong barrier to horizontal transfer. Bioinformatics and preliminary experimental work has identified many candidate ard genes and we will take a structural genomics approach to their analysis utilising high-throughput cloning, expression and crystallisation techniques to maximise our chances of achieving our goals, namely, the genetic, biochemical and structural understanding of at least two representatives of each of the ArdA and ArdB protein families. Of particular interest is the prediction that the Ard proteins may be structural and electrostatic mimics of the DNA recognised and bound by restriction enzymes as recently demonstrated by us for another, unrelated antirestriction protein.