Waugh D S, Sauer R T
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Proc Natl Acad Sci U S A. 1993 Oct 15;90(20):9596-600. doi: 10.1073/pnas.90.20.9596.
Single alanine substitution mutations at Asp-450 or Asp-467 of the type IIS restriction enzyme Fok I have no effect on the ability of the enzyme to bind strongly and selectively to its recognition site but completely eliminate its ability to cleave either strand of substrate DNA. Since wild-type Fok I shows no kinetic preference or required order of strand cleavage, these results indicate that Fok I, which evidently functions as a monomer, uses a single catalytic center to cleave both strands of DNA. In this respect, Fok I may resemble other monomeric enzymes that cleave double-stranded DNA.
IIS型限制性内切酶Fok I的天冬氨酸-450或天冬氨酸-467位点发生单个丙氨酸取代突变，对该酶与识别位点紧密且选择性结合的能力没有影响，但完全消除了其切割底物DNA任何一条链的能力。由于野生型Fok I没有动力学偏好或链切割的特定顺序，这些结果表明，显然作为单体发挥作用的Fok I利用单个催化中心切割DNA的两条链。在这方面，Fok I可能类似于其他切割双链DNA的单体酶。
