HIV relationship tree based on molecular function. All the virus IDs shown in the figure are Uniprot IDs. The length of each branch represents the distance between different viruses. HIV-1 and HIV-2 virus are almost completely separated, except HV1LA, which belongs to the HIV-1 group M subgroup B and is grouped with the HIV-2 virus, and HV2KR falls in the HIV-1 virus clade. SIVM1, which represents the simian immunodeficiency virus, shows closer relationship with HIV-2 virus. Meanwhile, HV192 has a little difference with other HIV-1 viruses in our figure. According to the graph, the distances among HIV-1 viruses are relatively farther than the distances between HIV-2 viruses.