Craspase Orthologs Cleave a Nonconserved Site in Target Protein Csx30
S.P.B. van Beljouw (TU Delft - BN/Stan Brouns Lab)
Anna C. van Eijkeren-Haagsma (TU Delft - BN/Stan Brouns Lab)
Konstantinos Kalogeropoulos (Technical University of Denmark (DTU))
Martin Pabst (TU Delft - BT/Environmental Biotechnology)
Stan J J Brouns (TU Delft - BN/Stan Brouns Lab)
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Abstract
The Craspase CRISPR-Cas effector consists of the RNA-guided ribonuclease gRAMP and the protease TPR-CHAT, coupling target RNA recognition to protease activation. The natural substrate of Craspase is Csx30, a protein cleaved in two fragments that subsequently activates downstream antiviral pathways. Here, we determined the protease substrate specificity of Craspase from Candidatus “Jettenia caeni” (Jc-Craspase). We find that Jc-Craspase cleaves Jc-Csx30 in a target RNA-dependent fashion in A|S, which is different from the sites found in two other studied Craspases (L|D and M|K for Candidatus “Scalindua brodae” and Desulfonema ishimotonii, respectively). The fact that Craspase cleaves a nonconserved site across orthologs indicates the evolution of specific protein interactions between Craspase and its respective Csx30 target protein. The Craspase family thus represents a panel of proteases with different substrate specificities, which we exploited for the development of a readout for multiplexed RNA detection.
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