Krüger D H, Presber W, Hansen S, Rosenthal H A
Z Allg Mikrobiol. 1977;17(8):581-91. doi: 10.1002/jobm.3630170802.
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.
噬菌体T3和T7在大肠杆菌原噬菌体P1存在的情况下，其细胞内生长受到限制。噬菌体T3比T7具有更高的表达其基因组和损伤宿主细胞的能力。T3对P1限制的这种部分保护作用归因于T3编码的S-腺苷甲硫氨酸酶（SAMase），该酶可降解S-腺苷甲硫氨酸，即P1限制内切核酸酶的辅助因子。由于我们在体内未观察到DNA切割现象，因此我们得出结论，P1核酸酶在体内的作用仅限于与T3和T7 DNA进行SAM依赖性的阻遏物样结合，而与DNA的进一步反应（修饰与切割）则被阻断。
