Department of Chemistry, Portland State University, OR 97207, USA.
J Mol Evol. 2010 Mar;70(3):233-41. doi: 10.1007/s00239-010-9325-3. Epub 2010 Mar 3.
An in vitro form of the self-splicing group-I intron interrupting the Azoarcus tRNA(Ile) was shortened by ~10% with the removal of helix P6a. This deletion reduced the reverse-splicing activity of the ribozyme about 10-fold. Through in vitro selection, this activity was restored in several low-error mutants. A number of mutations were found that improved reverse-splicing activity through both increased k (obs) and better folding. The deletion mutant could be fragmented into as many as three discrete pieces, which, when incubated together, were capable of covalent self-assembly through energy-neutral transesterification reactions, a process called autorecombination. A subset of the mutations identified through in vitro selection for reverse-splicing were exaptations in that they were also shown to augment the autorecombination reactions, leading to higher yields of covalently self-assembled products, making this the smallest such system yet discovered.
体外自剪接组 I 内含子的一种形式通过去除 P6a 螺旋将自身缩短了约 10%。该缺失使核酶的反向剪接活性降低了约 10 倍。通过体外选择，在几个低错误突变体中恢复了该活性。发现了许多突变，通过增加 k（obs）和更好的折叠提高了反向剪接活性。缺失突变体可以被分割成多达三个离散的片段，这些片段在孵育时可以通过能量中性的酯交换反应进行共价自组装，这一过程称为自重组。通过体外选择反向剪接来鉴定的一组突变是适应，因为它们也被证明可以增强自重组反应，从而产生更高产量的共价自组装产物，这使得该系统成为迄今为止发现的最小的系统。
