Protein Family Models

Cas9, originally named Csn1, is the large, multifunctional signature protein of type II CRISPR/Cas systems. It is well known even to general audiences because its RNA-guided endonuclease activity has made it a popular tool for custom editing of eukaryotic genomes.

Gene:

cas9

Date:

2024-01-12

Cas9-BH is the bridge helix between the NUC and the REC lobes of Cas9 - the CRISPR-associated endonuclease Cas9. The REC lobe and the NUC lobe of Cas9 fold to present a positively charged groove at their interface which accommodates the negatively charged sgRNA:target DNA heteroduplex [1]. CRISPR (clustered regularly interspaced short palindromic repeat)-Cas system occurs naturally in bacteria as a defence against invasion by phages or other mobile genetic elements. Cas9 is targeted to specific genomic locations by sgRNAs or single guide RNAs, in order to complex with invading DNA in order to cleave it and render it inactive. [1]. 24529477. Crystal Structure of Cas9 in Complex with Guide RNA and Target. DNA.. Nishimasu H, Ran FA, Hsu PD, Konermann S, Shehata SI, Dohmae N,. Ishitani R, Zhang F, Nureki O;. Cell. 2014; [Epub ahead of print] (from Pfam)

Date:

2024-04-03

Cas9 proteins are abundant across the bacterial kingdom, but vary widely in both sequence and size. All known Cas9 enzymes contain an HNH domain that cleaves the DNA strand complementary to the guide RNA sequence (target strand), and a RuvC nuclease domain required for cleaving the noncomplementary strand (non-target strand), yielding double-strand DNA breaks (DSBs). The crystal structures of type II-A and II-C Cas9 proteins highlight the features in Cas9 enzymes that support their function as RNA-guided endonucleases. Cas9 enzymes adopt a bilobed architecture composed of a nuclease lobe containing juxtaposed RuvC and HNH nuclease domains and a variable alpha-helical lobe likely to be involved in nucleic acid binding. The RuvC domain forms the structural core of the nuclease lobe, a six-stranded beta sheet surrounded by four alpha helices, with all three conserved subdomains (I, II, III) contributing catalytic residues to the active site [1]. [1]. 24505130. Structures of Cas9 endonucleases reveal RNA-mediated. conformational activation.. Jinek M, Jiang F, Taylor DW, Sternberg SH, Kaya E, Ma E, Anders. C, Hauer M, Zhou K, Lin S, Kaplan M, Iavarone AT, Charpentier E,. Nogales E, Doudna JA;. Science. 2014;343:1247997. (from Pfam)

Date:

2024-04-03

This HNH nuclease domain is found in CRISPR-related proteins. (from Pfam)

Date:

2023-12-12