Computer model of lamellarin D (LAM-D) bound to the covalent topoisomerase I-DNA complex. The drug is shown in the center as a CPK model at the interface between the DNA (with the double helix backbones colored in blue) and the protein (with a(alpha)-helices in red and (b(beta)- sheets in yellow). The model is derived from the topotecan-DNA-topoisomerase crystallographic model. Topotecan was replaced with LAM-D and the structure of the resulting ternary complex was minimized. LAM-D intercalates at the site of DNA cleavage stabilized with both the flanking base pairs forming stacking interactions. For details, see the article by Facompre´ et al. on p. 7392 of this issue.