5kk5
From Proteopedia
AsCpf1(E993A)-crRNA-DNA ternary complex
Structural highlights
FunctionCS12A_ACISB 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). Recognizes a short motif in the CRISPR repeat sequences (the 5' PAM or protospacer adjacent motif, TTTN in this organism) to help distinguish self versus nonself, as targets within the bacterial CRISPR locus do not have PAMs (PubMed:26422227). Has dsDNA endonuclease activity, results in staggered 4-base 5' overhangs 19 and 22 bases downstream of the PAM on the non-targeted and targeted strand respectively (PubMed:26422227). Non-target strand cleavage by the RuvC domain is probably a prerequisite of target strand cleavage by the Nuc domain (PubMed:27114038). In this CRISPR system correct processing of pre-crRNA requires only this protein and the CRISPR locus (By similarity).[UniProtKB:A0Q7Q2][1] [2] Publication Abstract from PubMedCRISPR-Cas9 and CRISPR-Cpf1 systems have been successfully harnessed for genome editing. In the CRISPR-Cas9 system, the preordered A-form RNA seed sequence and preformed protein PAM-interacting cleft are essential for Cas9 to form a DNA recognition-competent structure. Whether the CRISPR-Cpf1 system employs a similar mechanism for target DNA recognition remains unclear. Here, we have determined the crystal structure of Acidaminococcus sp. Cpf1 (AsCpf1) in complex with crRNA and target DNA. Structural comparison between the AsCpf1-crRNA-DNA ternary complex and the recently reported Lachnospiraceae bacterium Cpf1 (LbCpf1)-crRNA binary complex identifies a unique mechanism employed by Cpf1 for target recognition. The seed sequence required for initial DNA interrogation is disordered in the Cpf1-cRNA binary complex, but becomes ordered upon ternary complex formation. Further, the PAM interacting cleft of Cpf1 undergoes an "open-to-closed" conformational change upon target DNA binding, which in turn induces structural changes within Cpf1 to accommodate the ordered A-form seed RNA segment. This unique mechanism of target recognition by Cpf1 is distinct from that reported previously for Cas9. Type V CRISPR-Cas Cpf1 endonuclease employs a unique mechanism for crRNA-mediated target DNA recognition.,Gao P, Yang H, Rajashankar KR, Huang Z, Patel DJ Cell Res. 2016 Aug;26(8):901-13. doi: 10.1038/cr.2016.88. Epub 2016 Jul 22. PMID:27444870[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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