小柯机器人

美国博德研究所张锋团队揭示OMEGA切口酶IsrB与ωRNA和靶标DNA复合的结构。该研究于2022年10月12日在线发表于国际一流学术期刊《自然》。

研究人员报告了Desulfovirgula thermocuniculi IsrB（DtIsrB）与其同源的ωRNA和靶标DNA复合的冷冻电镜结构。研究人员发现IsrB蛋白的整体结构与Cas9有一个共同的支架。然而，与Cas9不同的是，Cas9使用一个识别（REC）叶来促进靶标的选择，而IsrB依靠它的ωRNA，其中的一部分形成一个复杂的三元结构，与REC的位置相似。对IsrB及其ωRNA的结构分析以及与其他RNA引导系统的比较突出了蛋白质和RNA之间的功能相互作用，并促进了人们对这些不同系统的生物学和演化的理解。

据介绍，RNA引导的系统，如CRISPR-Cas，结合了可编程的底物识别和酶的功能，这种结合已经被有利地用于开发强大的分子技术。这些系统的结构研究阐明了RNA和蛋白质如何共同识别和切割它们的底物，指导了进一步技术开发的合理工程。最近的工作确定了一类新的RNA引导系统，称为OMEGA，其中包括IscB，可能是Cas9的祖先，以及切口酶IsrB，这是IscB的同源物，其缺乏HNH核酸酶结构域。IsrB仅由大约350个氨基酸组成，但其小尺寸被相对较大的RNA向导（大约300-nt ωRNA）所抵消。

附：英文原文

Title: Structure of the OMEGA nickase IsrB in complex with ωRNA and target DNA

Author: Hirano, Seiichi, Kappel, Kalli, Altae-Tran, Han, Faure, Guilhem, Wilkinson, Max E., Kannan, Soumya, Demircioglu, F. Esra, Yan, Rui, Shiozaki, Momoko, Yu, Zhiheng, Makarova, Kira S., Koonin, Eugene V., Macrae, Rhiannon K., Zhang, Feng

Issue&Volume: 2022-10-12

Abstract: RNA-guided systems, such as CRISPR–Cas, combine programmable substrate recognition with enzymatic function, a combination that has been used advantageously to develop powerful molecular technologies1,2. Structural studies of these systems have illuminated how the RNA and protein jointly recognize and cleave their substrates, guiding rational engineering for further technology development3. Recent work identified a new class of RNA-guided systems, termed OMEGA, which include IscB, the likely ancestor of Cas9, and the nickase IsrB, a homologue of IscB lacking the HNH nuclease domain4. IsrB consists of only around 350 amino acids, but its small size is counterbalanced by a relatively large RNA guide (roughly 300-nt ωRNA). Here, we report the cryogenic-electron microscopy structure of Desulfovirgula thermocuniculi IsrB (DtIsrB) in complex with its cognate ωRNA and a target DNA. We find the overall structure of the IsrB protein shares a common scaffold with Cas9. In contrast to Cas9, however, which uses a recognition (REC) lobe to facilitate target selection, IsrB relies on its ωRNA, part of which forms an intricate ternary structure positioned analogously to REC. Structural analyses of IsrB and its ωRNA as well as comparisons to other RNA-guided systems highlight the functional interplay between protein and RNA, advancing our understanding of the biology and evolution of these diverse systems.

DOI: 10.1038/s41586-022-05324-6

Source: https://www.nature.com/articles/s41586-022-05324-6

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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