Determination of the 5'-terminal sequences flanking all the individual cleavage sites for endonuclease AvaI in bacteriophage-lambda DNA has shown that this enzyme recognizes the hexanucleotide sequences: (Formula: see text), This sequence is cut as shown by the arrows to give single-stranded 5'-tetranucleotide protrusions (cohesive ends). Endonucleases SmaI, XhoI and XmaI recognize different symmetrical subsets of this sequence and provide independent evidence for the occurrence of these subsets at particular endonuclease-AvaI cleavage sites in the bacteriophage-lambda genome. Further evidence for this structure came from the demonstration that DNA fragments generated by endonuclease AvaI can be ligated to form a discrete set of larger molecules and from nearest-neighbor analysis which showed that cytosine residues occurred at the 3'-side of cleavage points. The observation that endonuclease AvaII recognized a subset of the sites recognized by AsuI [Hughes, Bruce & Murray (1979) Biochem. J. 185, 59-63[ led to the deduction that AvaII recognize the pentanucleotide sequence: (Formula: see text), and breaks internucleotide bonds at the positions indicated by the arrows.
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机译：确定噬菌体λDNA中核酸内切酶AvaI的所有单个切割位点侧翼的5'端序列已表明，该酶识别六核苷酸序列：（分子式：见正文），如箭头所示切割该序列，得到单链5'-四核苷酸突出（内聚末端）。内切核酸酶SmaI，XhoI和XmaI识别该序列的不同对称子集，并为这些子集在噬菌体-λ基因组中特定内切核酸酶-AvaI切割位点的发生提供了独立的证据。这种结构的进一步证据来自证明核酸内切酶AvaI产生的DNA片段可以连接形成离散的较大分子组的证据，以及来自最近邻分析的结果，该分析表明胞嘧啶残基出现在裂解点的3'侧。核酸内切酶AvaII识别被AsuI识别的位点的一个子集的观察[Hughes，Bruce＆Murray（1979）Biochem。 J. 185，59-63 [导致推论，AvaII识别五核苷酸序列：（分子式：见正文），并在箭头所示的位置断裂核苷酸间键。
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