FIG. 1.

Ribbon diagrams of the structures of HIV-1 IN fragments. The N-terminal domain of HIV IN is shown on the left. It is based upon PDB file 1WJA (11), coordinating a single zinc cation (black sphere) by using the HHCC motif. This motif consists of residues His12, His16, Cys40, and Cys43, depicted as black sticks. The core domain, center, is based upon 1B14 (68), showing the active form of the HIV IN catalytic domain. The active site has a D,D(35)E motif. Residues Asp116, Asp64, and Glu152 are depicted as black sticks, in order from left to right. Side chains of the two Asp residues bind a single magnesium cation, shown here as a black sphere. The C-terminal DNA binding domain is based upon coordinates in PDB file 1IHV (65). The N- and C-terminal domains were solved by NMR; the catalytic core domain was solved by X-ray diffraction.