title: The crystal structure of the CRISPR-associated protein Csn2 from Streptococcus agalactiae.
abstract: The prokaryotic immune system, CRISPR, confers an adaptive and inheritable defense mechanism against invasion by mobile genetic elements. Guided by small CRISPR RNAs (crRNAs), a diverse family of CRISPR-associated (Cas) proteins mediates the targeting and inactivation of foreign DNA. Here, we demonstrate that Csn2, a Cas protein likely involved in spacer integration, forms a tetramer in solution and structurally possesses a ring-like structure. Furthermore, co-purified Ca(2+) was found important for the DNA binding property of Csn2, which contains a helicase fold, with highly conserved DxD and RR motifs found throughout Csn2 proteins. We could verify that Csn2 binds ds-DNA. In addition molecular dynamics simulations suggested a Csn2 conformation that can "sit" on the DNA helix and binds DNA in a groove on the outside of the ring.
authors.affiliation: Institute of Biochemistry, Heinrich Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Ellinger
authors.forename: Zihni
authors.initials: Z
authors.lastname: Arslan
authors.forename: Reinhild
authors.initials: R
authors.lastname: Wurm
authors.forename: Britta
authors.initials: B
authors.lastname: Tschapek
authors.forename: Colin
authors.initials: C
authors.lastname: MacKenzie
authors.forename: Klaus
authors.initials: K
authors.lastname: Pfeffer
authors.forename: Santosh
authors.initials: S
authors.lastname: Panjikar
authors.forename: Rolf
authors.initials: R
authors.lastname: Wagner
authors.forename: Lutz
authors.initials: L
authors.lastname: Schmitt
authors.forename: Holger
authors.initials: H
authors.lastname: Gohlke
authors.forename: Ümit
authors.initials: Ü
authors.lastname: Pul
authors.forename: Sander H J
authors.initials: SH
authors.lastname: Smits
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray / Q000379:methods*; D004247:DNA / Q000378:metabolism; D011485:Protein Binding; D013292:Streptococcus agalactiae / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004247:DNA