title: Essential structural and functional roles of the Cmr4 subunit in RNA cleavage by the Cmr CRISPR-Cas complex.
abstract: The Cmr complex is the multisubunit effector complex of the type III-B clustered regularly interspaced short palindromic repeats (CRISPR)-Cas immune system. The Cmr complex recognizes a target RNA through base pairing with the integral CRISPR RNA (crRNA) and cleaves the target at multiple regularly spaced locations within the complementary region. To understand the molecular basis of the function of this complex, we have assembled information from electron microscopic and X-ray crystallographic structural studies and mutagenesis of a complete Pyrococcus furiosus Cmr complex. Our findings reveal that four helically packed Cmr4 subunits, which make up the backbone of the Cmr complex, act as a platform to support crRNA binding and target RNA cleavage. Interestingly, we found a hook-like structural feature associated with Cmr4 that is likely the site of target RNA binding and cleavage. Our results also elucidate analogies in the mechanisms of crRNA and target molecule binding by the distinct Cmr type III-A and Cascade type I-E complexes.
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Nancy F
authors.initials: NF
authors.lastname: Ramia
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Spilman
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tang
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Yaming
authors.initials: Y
authors.lastname: Shao
authors.affiliation: Departments of Biochemistry and Molecular Biology, Genetics, and Microbiology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Elmore
authors.affiliation: Departments of Biochemistry and Molecular Biology, Genetics, and Microbiology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Caryn
authors.initials: C
authors.lastname: Hale
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Alexis
authors.initials: A
authors.lastname: Cocozaki
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Nilakshee
authors.initials: N
authors.lastname: Bhattacharya
authors.affiliation: Departments of Biochemistry and Molecular Biology, Genetics, and Microbiology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Terns
authors.affiliation: Departments of Biochemistry and Molecular Biology, Genetics, and Microbiology, University of Georgia, Athens, GA 30602, USA. Electronic address: mterns@bmb.uga.edu.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Terns
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA. Electronic address: hong.li@fsu.edu.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA. Electronic address: sstagg@fsu.edu.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Stagg
mesh_terms: D019943:Amino Acid Substitution; D019843:Archaeal Proteins / Q000737:chemistry* / Q000502:physiology; D064130:CRISPR-Associated Proteins / Q000502:physiology; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D018360:Crystallography, X-Ray; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000502:physiology; D008958:Models, Molecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000502:physiology; D020027:Pyrococcus furiosus; D059367:RNA Cleavage
chemical_list: D019843:Archaeal Proteins; D064130:CRISPR-Associated Proteins; D026901:Membrane Transport Proteins; D021122:Protein Subunits