Putative methyltransferase. (Microbial infection) May be involved in the assembly and release stages of hepatitis C virus (HCV) life cycle and thus play a crucial role in HCV propagation. (Microbial infection) Interacts with HCV non-structural protein 4B/NS4B (via C-terminal region); this interaction may promote the recruitment of NS4B in the proximity of lipid droplet. Self-associates. Inserted in the ER membrane and migrates from the inserted site to lipid droplet. Belongs to the methyltransferase superfamily.