A further area of investigation involved DNA replication and recombination proteins in the model archaeal system Haloferax volcanii. In addition to providing an attractive model system for dissecting DNA replication and repair in eukaryotes, analysis of H. volcanii proteins  allowed us to further understand how these proteins have adapted to function in very high salt levels that would normally disrupt protein-DNA interactions (Winter and Bunting, 2012).

In order for these organisms to survive in high salt environments, such as the Dead Sea, they maintain very high intracellular salt concentrations and their proteins must function under these conditions. Frequent adaptations include an alteration in amino acid usage to present an acidic surface (right), surface bound ions (right) and an increase in inter-molecular salt bridges to stabilise multimeric proteins. Understanding such adaptation is of interest in biotechnology for processes in extreme conditions.

Our structure of the H. volcanii processivity factor, PCNA, demonstrates that the overall architecture is very similar to other PCNAs but is strikingly different with respect to charge distribution (Winter et al., 2009). All other PCNAs have an electropositive pore to prevent repulsion with the DNA backbone. Whilst H. volcanii PCNA lacks this electropositive surface it compensates by binding cations, which are visualised in the structure.

We additionally explored halophilic adaptation with respect to DNA binding in other key replication proteins that bind DNA directly (Winter et al. 2012).