Human DNA Ligase I bound to DNA (1X9N)
from Pascal, J. M., O'Brien, P. J., Tomkinson, A. E., Ellenberger, T.: Human DNA Ligase I Completely Encircles and Partially Unwinds Nicked DNA. Nature 432 pp. 473 (2004).
See the protein databank for more structures.
Chemistry 108: Essentials of organic and biochemistry