title: Electron microscopy studies of Type III CRISPR machines in Sulfolobus solfataricus.
abstract: The CRISPR (clustered regularly interspaced short palindromic repeats) system is an adaptive immune system that targets viruses and other mobile genetic elements in bacteria and archaea. Cells store information of past infections in their genome in repeat-spacer arrays. After transcription, these arrays are processed into unit-length crRNA (CRISPR RNA) that is loaded into effector complexes encoded by Cas (CRISPR-associated) genes. CRISPR-Cas complexes target invading nucleic acid for degradation. CRISPR effector complexes have been classified into three main types (I-III). Type III effector complexes share the Cas10 subunit. In the present paper, we discuss the structures of the two Type III effector complexes from Sulfolobus solfataricus, SsoCSM (subtype III-A) and SsoCMR (subtype III-B), obtained by electron microscopy and single particle analysis. We also compare these structures with Cascade (CRISPR-associated complex for antiviral defence) and with the RecA nucleoprotein.
authors.affiliation: *Institute of Structural Molecular Biology and Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3JR, U.K.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cannone
authors.forename: Mariam
authors.initials: M
authors.lastname: Webber-Birungi
authors.forename: Laura
authors.initials: L
authors.lastname: Spagnolo
mesh_terms: D064113:CRISPR-Cas Systems / Q000235:genetics; D064112:Clustered Regularly Interspaced Short Palindromic Repeats / Q000235:genetics*; D008854:Microscopy, Electron; D048229:Sulfolobus solfataricus / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure*