6vqx
From Proteopedia
Type I-F CRISPR-Csy complex with its inhibitor AcrF6
Structural highlights
Function[CSY1_PSEAB] CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Cas3 and Cascade participate in CRISPR interference, the third stage of CRISPR immunity (Potential). Involved in crRNA production or stability. The Csy ribonucleoprotein complex binds target ssDNA with high affinity but target dsDNA with much lower affinity.[1] [2] [CAS6_PSEAB] CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Processes pre-crRNA into individual crRNA units. Absolutely required for crRNA production or stability. Upon expression in E.coli endonucleolytically processes pre-crRNA, although disruption and reconstitution experiments indicate that in situ other genes are also required for processing. Yields 5'-hydroxy and 3'-phosphate groups. The Csy ribonucleoprotein complex binds target ssDNA with high affinity but target dsDNA with much lower affinity.[3] [4] [5] Publication Abstract from PubMedProkaryotes and viruses have fought a long battle against each other. Prokaryotes use CRISPR-Cas-mediated adaptive immunity, while conversely, viruses evolve multiple anti-CRISPR (Acr) proteins to defeat these CRISPR-Cas systems. The type I-F CRISPR-Cas system in Pseudomonas aeruginosa requires the crRNA-guided surveillance complex (Csy complex) to recognize the invading DNA. Although some Acr proteins against the Csy complex have been reported, other relevant Acr proteins still need studies to understand their mechanisms. Here, we obtain three structures of previously unresolved Acr proteins (AcrF9, AcrF8, and AcrF6) bound to the Csy complex using electron cryo-microscopy (cryo-EM), with resolution at 2.57 A, 3.42 A, and 3.15 A, respectively. The 2.57-A structure reveals fine details for each molecular component within the Csy complex as well as the direct and water-mediated interactions between proteins and CRISPR RNA (crRNA). Our structures also show unambiguously how these Acr proteins bind differently to the Csy complex. AcrF9 binds to key DNA-binding sites on the Csy spiral backbone. AcrF6 binds at the junction between Cas7.6f and Cas8f, which is critical for DNA duplex splitting. AcrF8 binds to a distinct position on the Csy spiral backbone and forms interactions with crRNA, which has not been seen in other Acr proteins against the Csy complex. Our structure-guided mutagenesis and biochemistry experiments further support the anti-CRISPR mechanisms of these Acr proteins. Our findings support the convergent consequence of inhibiting degradation of invading DNA by these Acr proteins, albeit with different modes of interactions with the type I-F CRISPR-Cas system. Inhibition mechanisms of AcrF9, AcrF8, and AcrF6 against type I-F CRISPR-Cas complex revealed by cryo-EM.,Zhang K, Wang S, Li S, Zhu Y, Pintilie GD, Mou TC, Schmid MF, Huang Z, Chiu W Proc Natl Acad Sci U S A. 2020 Mar 13. pii: 1922638117. doi:, 10.1073/pnas.1922638117. PMID:32170016[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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Categories: Large Structures | Chiu, W | Huang, Z | Li, S | Pintilie, G | Zhang, K | Zhu, Y | Acrf6 | Anti-crispr | Crispr | Csy | Rna binding protein-rna-inhibitor complex | Type i-f
