THE TD INTRON ENDONUCLEASE I-TEVI MAKES EXTENSIVE SEQUENCE-TOLERANT CONTACTS ACROSS THE MINOR GROOVE OF ITS DNA TARGET
THE TD INTRON ENDONUCLEASE I-TEVI MAKES EXTENSIVE SEQUENCE-TOLERANT CONTACTS ACROSS THE MINOR GROOVE OF ITS DNA TARGET
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DOI：
10.1002/j.1460-2075.1993.tb05862.x
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发表时间：
1993-05-01
期刊：
影响因子：
11.4
通讯作者：
BELFORT, M
中科院分区：
文献类型：
--
作者：
BRYK, M;QUIRK, SM;BELFORT, M
I-TevI 是一种由噬菌体 T4 的移动 td 内含子编码的双链 DNA 核酸内切酶，对无内含子 td 等位基因具有特异性。遗传和物理研究表明，该酶与其 DNA 底物在至少三个螺旋圈和螺旋圆周上广泛接触。值得注意的是，包含该相互作用结构域的 48 bp 区域内没有任何单个核苷酸对于切割是必需的。尽管两个子结构域（DI 和 DII）包含首选序列，但第三个结构域（DIII，与酶接触的主要区域）显示出低得多的序列偏好。白色 DII 和 DIII 足以识别和结合 I-TevI，所有三个结构域对于形成具有裂解能力的复合物都很重要。突变、足迹和干扰研究表明， I-TevI 穿过 DNA 的小沟和磷酸盐主链。接触似乎不是在单核苷酸水平上；相反，暗示了冗余的相互作用和/或结构识别。这些不寻常的特性为理解 I-TevI 如何识别 T-even 噬菌体 DNA 提供了基础，该 DNA 在主沟中被大量修饰。这些识别特征可能会增加可利用的天然基质的范围 核酸内切酶，从而扩展了移动内含子的侵入潜力。
I-TevI, a double-strand DNA endonuclease encoded by the mobile td intron of phage T4, has specificity for the intronless td allele. Genetic and physical studies indicate that the enzyme makes extensive contacts with its DNA substrate over at least three helical turns and around the circumference of the helix. Remarkably, no single nucleotide within a 48 bp region encompassing this interaction domain is essential for cleavage. Although two subdomains (DI and DII) contain preferred sequences, a third domain (DIII, a primary region of contact with the enzyme, displays much lower sequence preference. White DII and DIII suffice for recognition and binding of I-TevI, all three domains are important for formation of a cleavage-competent complex. Mutational, footprinting and interference studies indicate predominant interactions of I-TevI across the minor groove and phosphate backbone of the DNA. Contacts appear not to be at the single nucleotide level; rather, redundant interactions and/or structural recognition are implied. These unusual properties provide a basis for understanding how I-TevI recognizes T-even phage DNA, which is heavily modified in the major groove. These recognition characteristics may increase the range of natural substrates available to the endonuclease, thereby extending the invasive potential of the mobile intron.