Accessory Mutations Maintain Stability in Drug-Resistant HIV-1 Protease

The underlying mechanisms driving the evolution of drug resistance in human immunodeficiency virus (HIV) are only partially understood. We investigated the evolutionary cost of the major resistance mutations in HIV-1 protease in terms of protein stability. The accumulation of resistance mutations destabilizes the protease, limiting further adaptation. From an analysis of clinical isolates, we identified specific accessory mutations that were able to restore the stability of the protease or even increase it beyond the wild-type baseline. Resistance mutations were also found to decrease the activity of HIV protease near neutral pH values, while incorporating stabilizing mutations improved the enzyme's pH tolerance. These findings help us to explain the prevalence of mutations located far from the active site and underscore the importance of protein stability during the evolution of drug resistance in HIV. [Display omitted] ► We examined changes in HIV protease stability caused by drug resistance mutations. ► The major resistance mutations V82A, I84V, and L90M decreased protein stability. ► Accessory mutations L10I, L63P, A71V, and V77I had a compensatory effect when combined with I84V. ► Lowered stability decreased enzymatic pH tolerance, which was improved by accessory mutations.