Kufel J, Kirsebom L A
Department of Microbiology, Biomedical Center, Uppsala, Sweden.
Proc Natl Acad Sci U S A. 1996 Jun 11;93(12):6085-90. doi: 10.1073/pnas.93.12.6085.
We have studied RNase P RNA (M1 RNA) cleavage of model tRNA precursors that are cleaved at two independent positions. Here we present data demonstrating that cleavage at both sites depends on the 2'-OH immediately 5' of the respective cleavage site. However, we show that the 2-amino group of a guanosine at the cleavage site plays a significant role in cleavage at one of these sites but not at the other. These data suggest that these two cleavage sites are handled differently by the ribozyme. This theory is supported by our finding that the cross-linking pattern between Ml RNA and tRNA precursors carrying 4-thioU showed distinct differences, depending on the location of the 4-thioU relative to the respective cleavage site. These findings lead us to suggest that different cleavage sites are aligned differently in the active site, possibly as a result of different binding modes of a substrate to M1 RNA. We discuss a model in which the interaction between the 3'-terminal "RCCA" motif (first three residues interact) of a tRNA precursor and M1 RNA plays a significant role in this process.
我们研究了核糖核酸酶P RNA（M1 RNA）对在两个独立位置被切割的模型tRNA前体的切割作用。在此，我们展示的数据表明，两个位点的切割均取决于各自切割位点紧邻5'端的2'-羟基。然而，我们发现切割位点处鸟苷的2-氨基在其中一个位点的切割中起重要作用，而在另一个位点则不然。这些数据表明，核酶对这两个切割位点的处理方式不同。我们的这一理论得到了以下发现的支持：携带4-硫尿嘧啶的M1 RNA与tRNA前体之间的交联模式存在明显差异，这取决于4-硫尿嘧啶相对于各自切割位点的位置。这些发现使我们提出，不同的切割位点在活性位点的排列方式不同，这可能是由于底物与M1 RNA的结合模式不同所致。我们讨论了一个模型，其中tRNA前体的3'-末端“RCCA”基序（前三个残基相互作用）与M1 RNA之间的相互作用在此过程中起重要作用。
