title: Different restriction of bacteriophages T3 and T7 by P1-lysogenic cells and the role of the T3-coded SAMase.
abstract: The intracellular growth of the phages T3 and T7 is restricted in the presence of the Escherichia coli prophage P1. Phage T3 has a higher ability to express its genome and to damage the host cell than T7. This partial protection of T3 against P1 restriction is due to the T3-coded SAMase, an enzyme which degrades S-adenosylmethionine, the cofactor of the P1 restriction endonuclease. Since we did not observe DNA cleavage in vivo, we conclude that the in vivo action of the P1 nuclease is limited to a SAM-dependent repressor-like binding to T3 and T7 DNA, while further reactions with the DNA (modification vs cleavage) are blocked.
mesh_terms: D003090:Coliphages / Q000502:physiology*; D004261:DNA Replication; D004267:DNA Viruses / Q000502:physiology; D004279:DNA, Viral / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005814:Genes, Viral; D006867:Hydrolases / Q000378:metabolism*; D008242:Lysogeny; D012328:RNA Viruses / Q000502:physiology; D012436:S-Adenosylmethionine
chemical_list: D004279:DNA, Viral; D012436:S-Adenosylmethionine; D006867:Hydrolases; D004720:Endonucleases; C019614:adenosylmethionine hydrolase