MxA/MX1/IFI78K [MD390]

Interferon-induced GTP-binding protein MxA (also known as MX1, IFI-78K, Interferon-induced protein p78, Myxovirus resistance 1) is encoded by the MX1 gene in human. The MxA proteins belong to the family of large GTPases and are highly homologous with dynamins within their GTP-binding domain. MxA proteins differ from small GTPases and heterotrimeric G proteins in features such as their large size (70–100 kDa), a relatively low affinity for GTP, and a high intrinsic rate of GTP hydrolysis. MxA proteins contain a highly conserved tripartite GTP-binding motif within the N-terminal G domain, while their less conserved C-terminal half serves different functions such as homooligomerization and association with binding partners. Two distinct regions of human MxA, a central interactive region (amino acids 372–540) and a C-terminal leucine zipper motif (amino acids 564–662), are responsible for intra- and intermolecular interactions. MxA/Mx1 is cytosolic, while two MxB/Mx forms exist, a 78 kDa nuclear form and a 76 kDa cytosolic form lacking the N-terminal nuclear localization signal (NLS). Mx proteins are induced by type I IFNs and possess important antiviral properties. Human MxA confers resistance against influenza virus and hantaviruses, including Seoul virus, Puumala virus, Hantaan virus, and Andes virus, in vitro. Human MxB is also reported to inhibit HIV-1 infection by reducing the level of integrated viral DNA.