Beese L S, Derbyshire V, Steitz T A
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
Science. 1993 Apr 16;260(5106):352-5. doi: 10.1126/science.8469987.
Klenow fragment of Escherichia coli DNA polymerase I, which was cocrystallized with duplex DNA, positioned 11 base pairs of DNA in a groove that lies at right angles to the cleft that contains the polymerase active site and is adjacent to the 3' to 5' exonuclease domain. When the fragment bound DNA, a region previously referred to as the "disordered domain" became more ordered and moved along with two helices toward the 3' to 5' exonuclease domain to form the binding groove. A single-stranded, 3' extension of three nucleotides bound to the 3' to 5' exonuclease active site. Although this cocrystal structure appears to be an editing complex, it suggests that the primer strand approaches the catalytic site of the polymerase from the direction of the 3' to 5' exonuclease domain and that the duplex DNA product may bend to enter the cleft that contains the polymerase catalytic site.
与双链DNA共结晶的大肠杆菌DNA聚合酶I的Klenow片段，将11个碱基对的DNA定位在一条与包含聚合酶活性位点的裂隙成直角且与3'至5'核酸外切酶结构域相邻的凹槽中。当该片段结合DNA时，先前称为“无序结构域”的区域变得更加有序，并与两条螺旋一起朝着3'至5'核酸外切酶结构域移动以形成结合凹槽。一条由三个核苷酸组成的单链3'延伸与3'至5'核酸外切酶活性位点结合。尽管这种共晶体结构似乎是一种编辑复合体，但它表明引物链从3'至5'核酸外切酶结构域的方向接近聚合酶的催化位点，并且双链DNA产物可能会弯曲以进入包含聚合酶催化位点的裂隙。
