This is the C-terminal domain found in ATP-Dependent DNA Ligase from Bacteriophage T7. This domain has no ligase activity, however together with the N-terminal domain they bind to double-stranded DNA consistent with the idea that the DNA-binding site is between the domains in the intact protein. Furthermore, although the fold of domain 2 is very similar to a number of other proteins that bind single-stranded DNA, this domain does not bind to single-stranded DNA but instead has a high affinity for double-stranded DNA [1].

1: Crystal structure of an ATP-dependent DNA ligase from bacteriophage T7. Subramanya HS, Doherty AJ, Ashford SR, Wigley DB; Cell 1996;85:607-615. PMID:8653795