biostudies-literaturePiya DTexas A&M UniversityNIGMS NIH HHSTexas A&M AgriLife Research399-412https://www.ebi.ac.uk/biostudies/studies/S-EPMC6011833biostudies-literatureUnknown105(3)Bacterial Type I restriction-modification (R-M) systems present a major barrier to foreign DNA entering the bacterial cell. The temperate phage P1 packages several proteins into the virion that protect the phage DNA from host restriction. Isogenic P1 deletion mutants were used to reconstitute the previously described restriction phenotypes associated with darA and darB. While P1ΔdarA and P1ΔdarB produced the expected phenotypes, deletions of adjacent genes hdf and ddrA also produced darA-like phenotypes and deletion of ulx produced a darB-like phenotype, implicating several new proteins of previously unknown function in the P1 dar antirestriction system. Interestingly, disruption of ddrB decreased P1's sensitivity to EcoB and EcoK restriction. Proteomic analysis of purified virions suggestMolecular microbiologyThe multicomponent antirestriction system of phage P1 is linked to capsid morphogenesis.PMC6011833R01 GM027099Young RGill JJPiya DVara LRussell WKfalseThe multicomponent antirestriction system of phage P1 is linked to capsid morphogenesis.Bacterial Type I restriction-modification (R-M) systems present a major barrier to foreign DNA entering the bacterial cell. The temperate phage P1 packages several proteins into the virion that protect the phage DNA from host restriction. Isogenic P1 deletion mutants were used to reconstitute the previously described restriction phenotypes associated with darA and darB. While P1ΔdarA and P1ΔdarB produced the expected phenotypes, deletions of adjacent genes hdf and ddrA also produced darA-like phenotypes and deletion of ulx produced a darB-like phenotype, implicating several new proteins of previously unknown function in the P1 dar antirestriction system. Interestingly, disruption of ddrB decreased P1's sensitivity to EcoB and EcoK restriction. Proteomic analysis of purified virions suggest2017-01-01T00:00:00Z2017 Aug2025-04-04T18:40:40.414Z2019-03-26T23:42:36ZS-EPMC60118332850939810.1111/mmi.13705