Birkenbihl R P, Kemper B
Institut für Genetik der Universität zu Köln, Germany.
EMBO J. 1998 Aug 3;17(15):4527-34. doi: 10.1093/emboj/17.15.4527.
Endonuclease VII (endo VII) is a Holliday structure-resolving enzyme of bacteriophage T4. Its activity depends on dimerization, DNA binding and hydrolysis of two phosphodiester bonds flanking the Holliday junction. We analysed the DNA-binding activity of truncated monomeric and covalently linked dimeric endo VII proteins. We show that both ends of endo VII are involved in DNA binding. In particular, the C-terminus of one subunit interacts with the N-terminus of the other subunit, constituting one DNA-binding site; the other two termini form the second binding site of the dimer. One binding site is sufficient to bind cruciform DNA. The concerted mechanism involving termini from different subunits ensures that only dimers bind to Holliday structures, thus providing two catalytic centres which introduce two cleavages in opposite strands. This is a precondition for precise resolution of Holliday structures.
核酸内切酶VII（endo VII）是噬菌体T4的一种Holliday结构解离酶。其活性取决于二聚化、DNA结合以及Holliday连接点两侧两个磷酸二酯键的水解。我们分析了截短的单体和共价连接的二聚体endo VII蛋白的DNA结合活性。我们发现endo VII的两端均参与DNA结合。具体而言，一个亚基的C末端与另一个亚基的N末端相互作用，构成一个DNA结合位点；另外两个末端形成二聚体的第二个结合位点。一个结合位点足以结合十字形DNA。涉及不同亚基末端的协同机制确保只有二聚体与Holliday结构结合，从而提供两个催化中心，在相反链上引入两个切割位点。这是精确解离Holliday结构的前提条件。
