Before revision:  While initially epistatic interactions are likely to constrain the evolvability of a protein, we find no evidence that the HIV-1 protease has reached its potential for adaptation after 9 years of adapting to a changing drug environment .
After revision:  While initially epistatic interactions are likely to constrain the evolvability of a protein, we find no evidence that the HIV-1 protease has reached its potential for evolution after 9 years of adapting to a changing drug environment .