据研究人员介绍，III-E型RNA靶向效应复合物（gRAMP/Cas7-11）与一个类似于caspase的蛋白（TPR-CHAT/Csx29）相关联，形成Craspase（CRISPR引导的caspase）。
研究人员使用Craspase的冷冻电镜快照来解释了它的靶标RNA切割和蛋白酶激活机制。延伸到导引RNA的5′区的靶标-向导配对取代了gRAMP中的门控环，这引发了广泛的构象接力，从而异构地校准蛋白酶催化，并打开一个氨基酸侧链-结合的口袋。研究人员进一步将Csx30定义为内源性蛋白底物，被RNA激活的Craspase位点特异性水解。这种蛋白酶的活性被gRAMP的靶标RNA切割所关闭，并且不被含有匹配的前间隔序列侧翼序列的RNA靶标激活。因此，研究人员认为，Craspase是一种具有自我调节能力的靶标RNA激活的蛋白酶。
附：英文原文
Title: Craspase is a CRISPR RNA-guided, RNA-activated protease
Author: Chunyi Hu, Sam P. B. van Beljouw, Ki Hyun Nam, Gabriel Schuler, Fran Ding, Yanru Cui, Alicia Rodríguez-Molina, Anna C Haagsma, Menno Valk, Martin Pabst, Stan J. J. Brouns, Ailong Ke
Issue&Volume: 2022-08-25
Abstract: The Type III-E RNA-targeting effector complex (gRAMP/Cas7-11) is associated with a caspase-like protein (TPR-CHAT/Csx29) to form Craspase (CRISPR-guided caspase). Here we use cryo-electron microscopy snapshots of Craspase to explain its target RNA cleavage and protease activation mechanisms. Target-guide pairing extending into the 5′ region of the guide RNA displaces a gating loop in gRAMP, which triggers an extensive conformational relay that allosterically aligns the protease catalytic dyad and opens an amino acid sidechain-binding pocket. We further define Csx30 as the endogenous protein substrate that is site-specifically proteolyzed by RNA-activated Craspase. This protease activity is switched off by target RNA cleavage by gRAMP, and is not activated by RNA targets containing a matching protospacer flanking sequence. We thus conclude that Craspase is a target RNA-activated protease with self-regulatory capacity.
DOI: add5064
Source: https://www.science.org/doi/10.1126/science.add5064