Systems of catalytic RNAs presumably gave rise to important evolutionary innovations, such as the genetic code. Such systems may exhibit particular tolerance to errors (error minimization) as well as coding specificity. While often assumed to result from natural selection, error minimization may instead be an emergent by-product. In an RNA world, a system of self-aminoacylating ribozymes could enforce the mapping of amino acids to anticodons. We measured the activity of thousands of ribozyme mutants on alternative substrates (activated analogs for tryptophan, phenylalanine, leucine, isoleucine, valine, and methionine). Related ribozymes exhibited shared preferences for substrates, indicating that adoption of additional amino acids by existing ribozymes would itself lead to error minimization. Furthermore, ribozyme activity was positively correlated with specificity, indicating that selection for increased activity would also lead to increased specificity. These results demonstrate that by-products of ribozyme evolution could lead to adaptive value in specificity and error tolerance.

催化 RNA 系统可能产生了重要的进化创新，例如遗传密码。这样的系统可能表现出对错误的特定容忍度（错误最小化）以及编码特异性。虽然通常假设错误最小化是自然选择的结果，但错误最小化可能反而是一个紧急的副产品。在 RNA 世界中，自氨酰化核酶系统可以强制将氨基酸映射到反密码子。我们测量了数千种核酶突变体在替代底物（色氨酸、苯丙氨酸、亮氨酸、异亮氨酸、缬氨酸和甲硫氨酸的活化类似物）上的活性。相关的核酶表现出对底物的共同偏好，表明现有核酶采用额外的氨基酸本身会导致错误最小化。此外，核酶活性与特异性呈正相关，表明选择增加活性的也会导致特异性增加。这些结果表明，核酶进化的副产品可能导致特异性和容错性方面的适应性价值。