Abstract
Type III CRISPR-Cas immunity is widespread in prokaryotes and is generally mediated by multisubunit effector complexes. These complexes recognize complementary viral transcripts and can activate ancillary immune proteins. Here, we describe a type III-E effector from Candidatus “Scalindua brodae” (Sb-gRAMP), which is natively encoded by a single gene with several type III domains fused together. This effector uses CRISPR RNA to guide target RNA recognition and cleaves single-stranded RNA at two defined positions six nucleotides apart. Sb-gRAMP physically combines with the caspase-like TPR-CHAT peptidase to form the CRISPR-guided caspase (Craspase) complex, suggesting a potential mechanism of target RNA–induced protease activity to gain viral immunity.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Bacteria / enzymology*
-
Bacteria / genetics*
-
Bacterial Proteins / chemistry
-
Bacterial Proteins / metabolism*
-
CRISPR-Associated Proteins / chemistry
-
CRISPR-Associated Proteins / genetics
-
CRISPR-Associated Proteins / metabolism*
-
CRISPR-Cas Systems*
-
Caspases / chemistry
-
Caspases / metabolism
-
Endoribonucleases / chemistry
-
Endoribonucleases / genetics
-
Endoribonucleases / metabolism*
-
Interspersed Repetitive Sequences
-
Peptide Hydrolases / chemistry
-
Peptide Hydrolases / metabolism*
-
Protein Domains
-
RNA, Bacterial / metabolism
-
RNA, Viral / metabolism
-
Substrate Specificity
Substances
-
Bacterial Proteins
-
CRISPR-Associated Proteins
-
RNA, Bacterial
-
RNA, Viral
-
Endoribonucleases
-
Peptide Hydrolases
-
Caspases