Interaction of the ocr gene 0.3 protein of bacteriophage T7 with EcoKI restriction/modification enzyme
Interaction of the ocr gene 0.3 protein of bacteriophage T7 with EcoKI restriction/modification enzyme
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DOI：
10.1093/nar/gkf518
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发表时间：
2002-09-15
影响因子：
14.9
通讯作者：
Dryden, DTF
中科院分区：
文献类型：
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作者：
Atanasiu, C;Su, TJ;Dryden, DTF
OCR蛋白是T7噬菌体基因0.3的产物，是B型DNA磷酸骨架的结构模拟物。它总共模拟了22个磷酸基团，类似于24个碱基对的DNA。这种模仿使它能够阻止I型DNA限制性内切酶与DNA的结合，并抑制这些酶。我们已经确定多个OCR二聚体可以化学计量地与原型I型酶EcoKI结合。一个二聚体与核心甲基转移酶结合，两个二聚体与完整的双功能限制和修饰酶结合。OCR还可以与EcoKI的组成亚基结合。与甲基转移酶核心的结合亲和力极强，具有较大的有利热变和不利的熵变。这种强烈的相互作用防止了甲基转移酶的解离，这种解离是在酶稀释时发生的。这种稳定是因为相互作用似乎涉及到OCR的几乎整个表面积，并导致酶完全包裹在OCR周围。
The ocr protein, the product of gene 0.3 of bacteriophage T7, is a structural mimic of the phosphate backbone of B-form DNA. In total it mimics 22 phosphate groups over similar to24 bp of DNA. This mimicry allows it to block DNA binding by type I DNA restriction enzymes and to inhibit these enzymes. We have determined that multiple ocr dimers can bind stoichiometrically to the archetypal type I enzyme, EcoKI. One dimer binds to the core methyltransferase and two to the complete bifunctional restriction and modification enzyme. Ocr can also bind to the component subunits of EcoKI. Binding affinity to the methyltransferase core is extremely strong with a large favourable enthalpy change and an unfavourable entropy change. This strong interaction prevents the dissociation of the methyltransferase which occurs upon dilution of the enzyme. This stabilisation arises because the interaction appears to involve virtually the entire surface area of ocr and leads to the enzyme completely wrapping around ocr.