APOBEC3G: A human protein that interferes with the replication of HIV by incorporating itself into virus particles and damaging the genetic material of the virus. The viral protein Vif can halt this process in two ways: (1) by binding to APOBEC3G and preventing it from incorporating into virus particles; and (2) by targeting APOBEC3G for destruction and almost completely eliminating it from the cell. APOBEC3G stands for apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G.