May be involved in the regulation of cell differentiation. Promotes intracellular multiplication of tobamoviruses, probably being a component of the replication complex. Homodimer. Constituent of tobamovirus replication complex (By similarity). Expressed in rosette leaves. Slightly reduced efficiency of intracellular multiplication of tobamoviruses (e.g. crucifer strain TMV-Cg), characterized by a reduced amplification of TMV-related RNAs. Belongs to the tetraspanin (TM4SF) family.