Shlomai J, Kornberg A
J Biol Chem. 1980 Jul 25;255(14):6794-8.
Protein n' of Escherichia coli is required for formation of the prepriming complex in replication of the single-stranded circle of phiX174 DNA. The protein, purified to near homogeneity, possesses ATPase (dATPase) activity in the presence of single-stranded, but not duplex, DNAs. Except for phiX174 DNA, ATPase activity is completely suppressed by coating the DNA with single strand binding protein (SSB). phiX174 DNA possesses a unique sequence with a potential hairpin structure that is recognized as an effector (Shlomai, J., and Kornberg, A. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 799-803). Sequences with secondary structure in SSB-coated M13 DNA which are recognized by RNA polymerase, and in coated G4 DNA by primase, are inert for protein n'. Approximately 30 of the 180 molecules of SSB bound to phiX DNA are destabilized by protein n' in an ATP-dependent reaction. These actions by protein n' may be important in recognizing an origin for forming the prepriming complex that leads to initiation of phiX complementary strand synthesis.
大肠杆菌的蛋白质n是形成phiX174 DNA单链环复制中的引发前复合体所必需的。该蛋白质纯化至接近均一，在单链而非双链DNA存在时具有ATP酶（dATP酶）活性。除phiX174 DNA外，通过用单链结合蛋白（SSB）包被DNA可完全抑制ATP酶活性。phiX174 DNA具有独特序列，带有潜在的发夹结构，该结构被识别为效应物（施洛迈，J.，和科恩伯格，A.（1980年）美国国家科学院院刊77，799 - 803）。在被SSB包被的M13 DNA中具有二级结构且被RNA聚合酶识别的序列，以及在被包被的G4 DNA中被引发酶识别的序列，对蛋白质n是无活性的。与phiX DNA结合的180个SSB分子中约30个在ATP依赖反应中被蛋白质n破坏稳定性。蛋白质n的这些作用对于识别形成引发前复合体的起始点可能很重要，该引发前复合体导致phiX互补链合成的起始。
