More than 35 million people around the world now live with HIV/AIDS. While drug discovery efforts to combat the disease have been successful, multiple treatments are required because the virus mutates and develops resistance to individual drugs. In fact, the HIV virus has evolved to evade the first line of defense—a protein called APOBEC3G, also known as A3G. Now, in a paper published last week in the journal Nature Chemistry, physics professor Mark Williams and his team present new research that elucidates a long-held paradox about these proteins that could transform HIV drug discovery.