Brown N L, Smith M
Proc Natl Acad Sci U S A. 1977 Aug;74(8):3213-6. doi: 10.1073/pnas.74.8.3213.
The nucleotide sequences in the replicative form (duplex) of phiX174 DNA around six sites cut by Hga I, a restriction endonuclease from Haemophilus gallinarum, have been compared. The enzyme produces a staggered cleavage resulting in a pentanucleotide 5'-terminal extension. The sequences within and immediately surrounding the pentanucleotide cleavage site have no obvious relationship. However, the sequence 5'-G-A-C-G-C-3' 3'-C-T-G-C-G-5' occurs five nucleotide pairs to the left of the cut in the upper strand and 10 nucleotide pairs to the left of the cut in the lower strand and, therefore, is believed to constitute the recognition site. This is a member of the class of restriction endonucleases in which recognition and cleavage sites lack 2-fold rotational symmetry. The method used to define the cleavage site is of general applicability.
已对鸡嗜血杆菌的限制性内切酶Hga I切割phiX174 DNA复制形式(双链体)的六个位点周围的核苷酸序列进行了比较。该酶产生交错切割,形成一个五核苷酸5'-末端延伸。五核苷酸切割位点内部及紧邻位点的序列没有明显关联。然而,序列5'-G-A-C-G-C-3' 3'-C-T-G-C-G-5' 在上链切割位点左侧五个核苷酸对处出现,在下链切割位点左侧十个核苷酸对处出现,因此被认为构成识别位点。这是一类识别位点和切割位点缺乏二重旋转对称性的限制性内切酶中的一员。用于确定切割位点的方法具有普遍适用性。