Project Summary The structural & dynamic basis for the interdependence of drug resistance Project 1 - Schiffer, UMASS Medical School In many drug resistance variants variants, multiple site mutations co-evolve to both decrease the affinity of a particular inhibitor and increase the viability and fitness of the enzyme. We hypothesize that the impact of particular mutations on conferring drug resistance is not simply additive, but that these mutations have a complex interdependent effect leading to viable variants that are highly resistant to existing drugs. As a project team we will test this hypothesis through a systematic and quantitative evaluation of the interdependency in drug resistance at the molecular level in HIV protease, through changes in the protease structure, thermodynamics, enzyme kinetics and dynamics by state-of-the-art experimental and computational techniques and apply this knowledge to develop inhibitors with high barrier to resistance. This data will identify residues and combinations of mutations that are pivotal signature sites in conferring drug resistance. Such a strategy is critical to revealing the complex molecular mechanisms of drug resistance, and both avoid resistance from the start and target highly resistant variants seen in clinic. This strategy will be directly applicable to other quickly evolving diseases where drug resistance thwarts effective therapy.