Protein evolution or engineering studies are traditionally focused on amino acid substitutions and the way these contribute to fitness. Meanwhile, the insertion and deletion of amino acids is often overlooked, despite being one of the most common sources of genetic variation. Recent methodological advances and successful engineering stories have demonstrated that the time is ripe for greater emphasis on these mutations and their understudied effects. This review highlights the evolutionary importance and biotechnological relevance of insertions and deletions (indels). We provide a comprehensive overview of approaches that can be employed to include indels in random, (semi)-rational or computational protein engineering pipelines. Furthermore, we discuss the tolerance to indels at the structural level, address how domain indels can link the function of unrelated proteins, and feature studies that illustrate the surprising and intriguing potential of frameshift mutations.

蛋白质进化或工程研究传统上侧重于氨基酸替代以及它们对健康的贡献方式。同时，氨基酸的插入和缺失经常被忽视，尽管它是最常见的遗传变异来源之一。最近的方法学进步和成功的工程案例表明，现在是时候更加重视这些突变及其未充分研究的影响了。这篇综述强调了插入和缺失（indels）的进化重要性和生物技术相关性。我们全面概述了可用于在随机、（半）有理或计算蛋白质工程管道中包含插入缺失的方法。此外，我们在结构层面讨论了对插入缺失的容忍度，