Bedford E, Tabor S, Richardson C C
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 1997 Jan 21;94(2):479-84. doi: 10.1073/pnas.94.2.479.
Bacteriophage T7 DNA polymerase shares extensive sequence homology with Escherichia coli DNA polymerase I. However, in vivo, E. coli DNA polymerase I is involved primarily in the repair of DNA whereas T7 DNA polymerase is responsible for the replication of the viral genome. In accord with these roles, T7 DNA polymerase is highly processive while E. coli DNA polymerase I has low processivity. The high processivity of T7 DNA polymerase is achieved through tight binding to its processivity factor, E. coli thioredoxin. We have identified a unique 76-residue domain in T7 DNA polymerase responsible for this interaction. Insertion of this domain into the homologous site in E. coli DNA polymerase I results in a dramatic increase in the processivity of the chimeric DNA polymerase, a phenomenon that is dependent upon its binding to thioredoxin.
噬菌体T7 DNA聚合酶与大肠杆菌DNA聚合酶I具有广泛的序列同源性。然而，在体内，大肠杆菌DNA聚合酶I主要参与DNA的修复，而T7 DNA聚合酶负责病毒基因组的复制。与这些作用相符的是，T7 DNA聚合酶具有高度的持续合成能力，而大肠杆菌DNA聚合酶I的持续合成能力较低。T7 DNA聚合酶的高持续合成能力是通过与它的持续合成因子——大肠杆菌硫氧还蛋白紧密结合来实现的。我们在T7 DNA聚合酶中鉴定出了一个负责这种相互作用的独特的76个氨基酸残基的结构域。将这个结构域插入大肠杆菌DNA聚合酶I的同源位点会导致嵌合DNA聚合酶的持续合成能力显著增加，这一现象依赖于它与硫氧还蛋白的结合。
