title: Bacteriophage T4-encoded Stp can be replaced as activator of anticodon nuclease by a normal host cell metabolite.
abstract: The bacterial tRNALys-specific anticodon nuclease is known as a phage T4 exclusion system. In the uninfected host cell anticodon nuclease is kept latent due to the association of its core protein PrrC with the DNA restriction-modification endonuclease EcoprrI. Stp, the T4-encoded peptide inhibitor of EcoprrI activates the latent enzyme. Previous in vitro work indicated that the activation by Stp is sensitive to DNase and requires added nucleotides. Biochemical and mutational data reported here suggest that Stp activates the latent holoenzyme when its EcoprrI component is tethered to a cognate DNA substrate. Moreover, the activation is driven by GTP hydrolysis, possibly mediated by the NTPase domain of PrrC. The data also reveal that Stp can be replaced as the activator of latent anticodon nuclease by certain pyrimidine nucleotides, the most potent of which is dTTP. The activation by dTTP likewise requires an EcoprrI DNA substrate and GTP hydrolysis but involves a different form of the latent holoenzyme/DNA complex. Moreover, whereas Stp relays its activating effect through EcoprrI, dTTP targets PrrC. The activation of the latent enzyme by a normal cell constituent hints that anticodon nuclease plays additional roles, other than warding off phage T4 infection.
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D017122:Bacteriophage T4 / Q000378:metabolism*; D004262:DNA Restriction Enzymes / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011742:Pyrimidine Nucleotides / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012260:Ribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000235:genetics / Q000378:metabolism; D013942:Thymine Nucleotides / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D020536:Enzyme Activators; D029968:Escherichia coli Proteins; D011742:Pyrimidine Nucleotides; D012346:RNA, Transfer, Amino Acyl; D013942:Thymine Nucleotides; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins; C094106:stp protein, Bacteriophage T4; D006160:Guanosine Triphosphate; C086510:DNA modification methylase EcoprrI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C084965:PrrC protein, E coli; D012260:Ribonucleases; C049345:anticodon nuclease; D004262:DNA Restriction Enzymes; C024157:thymidine 5'-triphosphate