The function of APOBEC3G (apolipoprotein B mRNA editing enzyme catalytic subunit 3G, ENSG00000239713) is as follows. DNA deaminase (cytidine deaminase) which acts as an inhibitor of retrovirus replication and retrotransposon mobility via deaminase- dependent and -independent mechanisms (PubMed:12808465, PubMed:16527742, PubMed:17121840, PubMed:18288108, PubMed:18849968, PubMed:19153609, PubMed:21123384, PubMed:22791714, PubMed:25542899). Exhibits potent antiviral activity against Vif-deficient HIV-1 (PubMed:12167863, PubMed:12859895, PubMed:14557625, PubMed:20219927, PubMed:21835787, PubMed:22807680, PubMed:22915799, PubMed:23097438, PubMed:23152537, PubMed:31397674). After the penetration of retroviral nucleocapsids into target cells of infection and the initiation of reverse transcription, it can induce the conversion of cytosine to uracil in the minus-sense single-strand viral DNA, leading to G-to-A hypermutations in the subsequent plus-strand viral DNA (PubMed:12808465, PubMed:12808466, PubMed:12809610, PubMed:12970355, PubMed:14528300, PubMed:22807680). The resultant detrimental levels of mutations in the proviral genome, along with a deamination-independent mechanism that works prior to the proviral integration, together exert efficient antiretroviral effects in infected target cells (PubMed:12808465, PubMed:12808466, PubMed:12809610, PubMed:12970355, PubMed:14528300). Selectively targets single-stranded DNA and does not deaminate double-stranded DNA or single- or double-stranded RNA (PubMed:12808465, PubMed:12809610, PubMed:12970355, PubMed:14528300). Exhibits antiviral activity also against simian immunodeficiency viruses (SIVs), hepatitis B virus (HBV), equine infectious anemia virus (EIAV), xenotropic MuLV-related virus (XMRV) and simian foamy virus (SFV) (PubMed:15031497, PubMed:16378963, PubMed:18448976, PubMed:19458006, PubMed:20335265). May inhibit the mobility of LTR and non-LTR retrotransposons (PubMed:16527742). {ECO:0000269|PubMed:12167863, ECO:0000269|PubMed:12808465, ECO:0000269|PubMed:12808466, ECO:0000269|PubMed:12809610, ECO:0000269|PubMed:12859895, ECO:0000269|PubMed:12970355, ECO:0000269|PubMed:14528300, ECO:0000269|PubMed:14557625, ECO:0000269|PubMed:15031497, ECO:0000269|PubMed:16378963, ECO:0000269|PubMed:16527742, ECO:0000269|PubMed:17121840, ECO:0000269|PubMed:18288108, ECO:0000269|PubMed:18849968, ECO:0000269|PubMed:19153609, ECO:0000269|PubMed:19458006, ECO:0000269|PubMed:20219927, ECO:0000269|PubMed:20335265, ECO:0000269|PubMed:21123384, ECO:0000269|PubMed:21835787, ECO:0000269|PubMed:22791714, ECO:0000269|PubMed:22807680, ECO:0000269|PubMed:22915799, ECO:0000269|PubMed:23097438, ECO:0000269|PubMed:23152537, ECO:0000269|PubMed:25542899, ECO:0000269|PubMed:31397674, ECO:0000303|PubMed:18448976}.