Cas5d protein processes pre-crRNA and assembles into a cascade-like interference complex in subtype I-C/Dvulg CRISPR-Cas system.
Publication Type:Journal Article
Source:Structure, Volume 20, Issue 9, p.1574-84 (2012)
Keywords:Bacillus, Bacterial Proteins, Base Sequence, Catalytic Domain, Consensus Sequence, Crystallography, X-Ray, Endoribonucleases, Escherichia coli, Genetic Complementation Test, Genetic Loci, Inverted Repeat Sequences, Models, Molecular, Protein Multimerization, Protein Structure, Secondary, Protein Subunits, RNA Cleavage, RNA Processing, Post-Transcriptional, RNA, Bacterial, Substrate Specificity, Surface Properties
<p>Clustered regularly interspaced short palindromic repeats (CRISPRs), together with an operon of CRISPR-associated (Cas) proteins, form an RNA-based prokaryotic immune system against exogenous genetic elements. Cas5 family proteins are found in several type I CRISPR-Cas systems. Here, we report the molecular function of subtype I-C/Dvulg Cas5d from Bacillus halodurans. We show that Cas5d cleaves pre-crRNA into unit length by recognizing both the hairpin structure and the 3' single stranded sequence in the CRISPR repeat region. Cas5d structure reveals a ferredoxin domain-based architecture and a catalytic triad formed by Y46, K116, and H117 residues. We further show that after pre-crRNA processing, Cas5d assembles with crRNA, Csd1, and Csd2 proteins to form a multi-sub-unit interference complex similar to Escherichia coli Cascade (CRISPR-associated complex for antiviral defense) in architecture. Our results suggest that formation of a crRNA-presenting Cascade-like complex is likely a common theme among type I CRISPR subtypes.</p>