Figure 4From: Crystal structure of an FIV/HIV chimeric protease complexed with the broad-based inhibitor, TL-3Changes in the packing contacts between the active site core and 90s loop. The reformation of the P1/P1' interaction of TL-3 and the 90s loop is aided by the loss of packing interactions between residue 37 in the active site and the 90s loop. In wild-type FIV protease (green) the side chain of Isoleucine 37 forms packing contacts with the side chains of Leucine 97 and Leucine 101, holding the 90s loop in position away from TL-3. The mutation of Isoleucine 37 to Valine, Leucine 97 to Threonine, and Leucine 101 to Isoleucine in the 12X mutant protease (yellow) eliminates these packing contacts, allowing the 90s loop to shift ~1.0Ã… toward the P1/P1' position of TL-3.Back to article page