Necessary for the efficient intracellular multiplication of tobamoviruses, probably being a membrane anchor promoting the formation of the replication complex. Constituent of tobamovirus replication complex. Interacts with TOM2A and with the helicase domain of tobamovirus-encoded replication proteins. Reduced efficiency of intracellular multiplication of tobamoviruses (e.g. crucifer strain TMV-Cg), characterized by a reduced accumulation of viral coat protein (CP) and reduced amplification of TMV-related RNAs. Belongs to the plant tobamovirus multiplication TOM1 protein family.