Werner M, Uhlenbeck O C
Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215, USA.
Nucleic Acids Res. 1995 Jun 25;23(12):2092-6. doi: 10.1093/nar/23.12.2092.
The ability of the hammerhead ribozyme to distinguish between matched and mismatched substrates was evaluated using two kinetically defined ribozymes that differed in the length and sequence of the substrate recognition helices. A mismatch in the innermost base pair of helix I affected k2, the chemical cleavage step, while more distal mismatches had no such effect. In contrast, mismatches in any of the four innermost base pairs of helix III affected k2. Chase experiments indicated that mismatches also increased the rate of substrate dissociation by at least 20-100-fold, as expected from the stabilities of RNA helices.
利用两种动力学定义的核酶评估锤头状核酶区分匹配和错配底物的能力，这两种核酶在底物识别螺旋的长度和序列上有所不同。螺旋I最内层碱基对的错配影响化学切割步骤k2，而更靠外的错配则没有这种影响。相比之下，螺旋III最内层四个碱基对中任何一个的错配都会影响k2。追踪实验表明，正如RNA螺旋稳定性所预期的那样，错配还会使底物解离速率至少提高20至100倍。
