Probing Charged Aminoacid Sidechains in Protein-Protein Interfaces Using NMR

Topoisomerase V from Kandleri plays an important dual role in DNA isomerization and repair. The 12 helix-hairpin-helix ((HhH)2) domains are responsible for DNA binding and for the AP lyase activity of the protein. Previous work in the Barrick lab on this system has shown that repeats can be expressed individually and in pairs, and Gdn-HCl-induced unfolding transitions can be fit using a global Ising fit to determine the intrinsic and interfacial free energies of the entire array. Both the intrinsic and interfacial free energies show a broad range of stabilities.