Inhibitor of viral RNA replication which confers resistance to some tobamoviruses including tobacco mild green mosaic virus (TMGMV) and pepper mild mottle virus (PMMoV), but not to tomato mosaic virus (ToMV strains L, ToMV0 and ToMV1-2) and tobacco mosaic virus (TMV) (PubMed:17699618, PubMed:3686829, PubMed:17238011, PubMed:19423673, PubMed:24299004). Prevents tobamoviruses RNA replication by affecting the association of tobamoviruses replication proteins (large and small subunits) with host membrane-associated proteins (e.g. TOM1, TOM2A and ARL8), thus inhibiting the replication complex formation on the membranes and avoiding viral negative-strand RNA synthesis (PubMed:19423673). Homodimer. (Microbial infection) Binds, via an ATP bridge, to the tobamoviruses avirulent (Avr) replication proteins (large and small subunits, e.g. tobacco mild green mosaic virus (TMGMV) AC P18339 and pepper mild mottle virus (PMMoV) AC P89657) to inhibit their function after the translation of tobamoviruses RNA, but before the viral replication complex formation on the membrane surfaces; this interaction is not possible with resistance-breaking strains replication proteins. The Tm-1 allele present in the tomato mosaic virus (ToMV)-resistant tomato cv. Craigella isolate GCR237 (AC A7M6E7) confers resistance to ToMV but not the allele present in the ToMV-susceptible tomato cv. Craigella isolate GCR26 (AC A7M6E8). Transgenic tobacco plants expressing tm-1 exhibit resistance to tobacco mild green mosaic virus (TMGMV) and pepper mild mottle virus (PMMoV), tobamoviruses that cannot multiply in tomato. Belongs to the UPF0261 family.