HIV-1 protease is a retroviral aspartyl protease (retropepsin) that is essential for the life-cycle of  HIV, the retrovirus that causes AIDS. HIV protease cleaves newly synthesized polyproteins at the appropriate places to create the mature protein components of an infectious HIV virion. Without effective HIV protease, HIV virions remain uninfectious. Thus, mutation of HIV protease's active site or inhibition of its activity disrupts HIV’s ability to replicate and infect additional cells, making HIV protease inhibition the subject of considerable pharmaceutical research.