Peebles C L, Zhang M, Perlman P S, Franzen J S
Department of Biological Sciences, University of Pittsburgh, PA 15260-7700, USA.
Proc Natl Acad Sci U S A. 1995 May 9;92(10):4422-6. doi: 10.1073/pnas.92.10.4422.
Domain 5 (D5) is a small hairpin structure within group II introns. A bimolecular assay system depends on binding by D5 to an intron substrate for self-splicing activity. In this study, mutations in D5 identify two among six nearly invariant nucleotides as being critical for 5' splice junction hydrolysis but unimportant for binding. A mutation at another site in D5 blocks binding. Thus, mutations can distinguish two D5 functions: substrate binding and catalysis. The secondary structure of D5 may resemble helix I formed by the U2 and U6 small nuclear RNAs in the eukaryotic spliceosome. Our results support a revision of the previously proposed correspondence between D5 and helix I on the basis of the critical trinucleotide 5'-AGC-3' present in both. We suggest that this trinucleotide plays a similar role in promoting the chemical reactions for both splicing systems.
结构域5（D5）是II组内含子中的一个小发夹结构。双分子检测系统依赖于D5与内含子底物的结合来实现自我剪接活性。在本研究中，D5中的突变确定了六个几乎不变的核苷酸中的两个对5'剪接连接水解至关重要，但对结合不重要。D5中另一个位点的突变会阻止结合。因此，突变可以区分D5的两种功能：底物结合和催化。D5的二级结构可能类似于真核剪接体中由U2和U6小核RNA形成的螺旋I。我们的结果支持基于两者中都存在的关键三核苷酸5'-AGC-3'对先前提出的D5与螺旋I之间对应关系进行修订。我们认为这个三核苷酸在促进两个剪接系统的化学反应中起类似作用。
