Suck D
Biological Structures and Biocomputing Programme, EMBL, Heidelberg, Germany.
J Mol Recognit. 1994 Jun;7(2):65-70. doi: 10.1002/jmr.300070203.
Bovine pancreatic DNase I shows a strong preference for double-stranded substrates and cleaves DNA with strongly varying cutting rates suggesting that the enzyme recognises sequence-dependent structural variations of the DNA double helix. The complicated cleavage pattern indicates that several local as well as global helix parameters influence the cutting frequency of DNase I at a given bond. The high resolution crystal structures of two DNase I-DNA complexes showed that the enzyme binds tightly in the minor groove, and to the sugar-phosphate backbones of both strands, and thereby induces a widening of the minor groove and a bending towards the major groove. In agreement with biochemical data this suggests that flexibility and minor groove geometry are major parameters determining the cutting rate of DNase I. Experimental observations showing that the sequence environment of a dinucleotide step strongly affects its cleavage efficiency can be rationalized by the fact that six base pairs are in contact with the enzyme. Mutational analysis based on the structural results has identified critical residues for DNA binding and cleavage and has lead to a proposal for the catalytic mechanism.
牛胰脱氧核糖核酸酶I对双链底物表现出强烈的偏好，并且以差异很大的切割速率切割DNA，这表明该酶能够识别DNA双螺旋的序列依赖性结构变异。复杂的切割模式表明，几个局部以及全局螺旋参数会影响给定键处脱氧核糖核酸酶I的切割频率。两种脱氧核糖核酸酶I-DNA复合物的高分辨率晶体结构表明，该酶紧密结合在小沟中，并与两条链的糖磷酸骨架结合，从而导致小沟变宽并向大沟弯曲。与生化数据一致，这表明灵活性和小沟几何形状是决定脱氧核糖核酸酶I切割速率的主要参数。实验观察表明，二核苷酸步的序列环境强烈影响其切割效率，这可以通过六个碱基对与该酶接触这一事实来解释。基于结构结果的突变分析确定了DNA结合和切割的关键残基，并提出了催化机制。
