Low R L, Cummings O W, King T C
Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110.
J Biol Chem. 1987 Nov 25;262(33):16164-70.
The purified endonuclease of bovine heart mitochondria shows a remarkable preference for a specific site in bovine mtDNA. This site was identified using a recombinant DNA template which includes a 4.9-kilobase portion of the 16-kilobase bovine mitochondrial sequence encompassing all of the displacement loop region. The endonucleolytic target corresponds to an evolutionarily conserved sequence tract of 12 consecutive guanine residues that is found in an otherwise highly divergent domain of the mitochondrial displacement loop region. The preference for this site is several hundred-fold greater than other less favored sites. Unlike other less prominent cleavage loci, the conserved sequence tract is readily nicked in either or both DNA strands, even at 0 degrees C. These findings suggest that there is a specific interaction of the endonuclease with this site in vivo that may be important for mtDNA replication.
纯化后的牛心线粒体核酸内切酶对牛线粒体DNA（mtDNA）中的特定位点表现出显著偏好。该位点是通过使用重组DNA模板鉴定出来的，该模板包含16千碱基牛线粒体序列中的4.9千碱基部分，涵盖了整个置换环区域。核酸内切酶的作用靶点对应于一段由12个连续鸟嘌呤残基组成的进化保守序列片段，该片段位于线粒体置换环区域一个其他部分高度分化的区域。对该位点的偏好比对其他较不偏好的位点高数百倍。与其他不太显著的切割位点不同，即使在0摄氏度时，保守序列片段在DNA的一条链或两条链上都很容易被切口。这些发现表明，核酸内切酶在体内与该位点存在特定相互作用，这可能对mtDNA复制很重要。
