Fig. 5: CapRelSJ46 can sense and respond to two unrelated trigger proteins in Bas11 phage.
From: A bacterial immunity protein directly senses two disparate phage proteins
a, Serial dilutions of the ancestral and evolved Bas11 phage spotted on lawns of cells harbouring either an EV or a plasmid producing CapRelSJ46. The corresponding genotypes of its MCP and Gp54 are indicated on the right. b, Serial dilutions of the indicated Bas11 phage spotted on lawns of cells harbouring either an EV or a plasmid producing CapRelSJ46. The corresponding genotypes of its MCP and Gp54 are indicated on the right. c, Left, schematics of the region encoding either Gp19 (the Gp54 homologue from SECΦ27) or the MCP. Right, serial dilutions of the indicated SECΦ27 phage spotted on lawns of cells harbouring either an EV or a plasmid producing CapRelSJ46. d, Summary of plaque-forming units (PFU) obtained for the ancestral SECΦ27 MCP(L114P) phage carrying Gp54Bas11 or eight escape clones, following spotting onto cells producing CapRelSJ46 or harbouring an EV. Three independent replicates are shown. *P = 10−18 (unpaired two-tailed t-test). e, Schematic of the gene 19 genomic region in SECΦ27 MCP(L114P) phage replaced by gene 54 from Bas11, with mutations in the escape clones from d labelled. f, Model for CapRelSJ46 activation. During infection, newly synthesized MCP and Gp54 bind the antitoxin domain of CapRelSJ46 to stabilize an active conformation; CapRelSJ46 then pyrophosphorylates (PPi) tRNAs to inhibit translation and restrict viral replication. g, Top, schematic of a conventional Red Queen dynamic between an antiviral immunity protein such as CapRelSJ46 and a single viral trigger protein, following the schematic in ref. 17. Bottom, when two proteins are recognized by an antiviral system like CapRelSJ46, viral escape is more difficult because any single escape mutation will not prevent activation of immunity.
