Amundsen S K, Taylor A F, Smith G R
Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, A1-162, PO Box 19024, Seattle, WA 98109, USA.
Nucleic Acids Res. 1998 May 1;26(9):2125-31. doi: 10.1093/nar/26.9.2125.
RecBCD enzyme acts in the major pathway of homologous recombination of linear DNA in Escherichia coli. The enzyme unwinds DNA and is an ATP-dependent double-strand and single-strand exonuclease and a single-strand endonuclease; it acts at Chi recombination hotspots (5'-GCTGGTGG-3') to produce a recombinogenic single-stranded DNA 3'-end. We found that a small RNA with a unique sequence of approximately 24 nt was tightly bound to RecBCD enzyme and co-purified with it. When added to native enzyme this RNA, but not four others, increased DNA unwinding and Chi nicking activities of the enzyme. In seven similarly active enzyme preparations the molar ratio of RNA molecules to RecBCD enzyme molecules ranged from 0.2 to <0.008. These results suggest that, although this unique RNA is not an essential enzyme subunit, it has a biological role in stimulating RecBCD enzyme activity.
RecBCD酶在大肠杆菌线性DNA同源重组的主要途径中发挥作用。该酶可解开DNA，是一种依赖ATP的双链和单链核酸外切酶以及单链核酸内切酶；它作用于Chi重组热点（5'-GCTGGTGG-3'）以产生具有重组活性的单链DNA 3'-末端。我们发现一种具有约24个核苷酸独特序列的小RNA与RecBCD酶紧密结合并与其共同纯化。当将这种RNA而非其他四种RNA添加到天然酶中时，会增加该酶的DNA解旋和Chi切口活性。在七种活性相似的酶制剂中，RNA分子与RecBCD酶分子的摩尔比范围为0.2至<0.008。这些结果表明，尽管这种独特的RNA不是必需的酶亚基，但它在刺激RecBCD酶活性方面具有生物学作用。
