Necessary for the efficient intracellular multiplication of tobamoviruses, being a component of the replication complex. Homodimer. Constituent of tobamovirus replication complex. Interacts with TOM1. Expressed in rosette leaves. 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.