title: Structural basis for processivity and single-strand specificity of RNase II.
abstract: RNase II is a member of the widely distributed RNR family of exoribonucleases, which are highly processive 3'-->5' hydrolytic enzymes that play an important role in mRNA decay. Here, we report the crystal structure of E. coli RNase II, which reveals an architecture reminiscent of the RNA exosome. Three RNA-binding domains come together to form a clamp-like assembly, which can only accommodate single-stranded RNA. This leads into a narrow, basic channel that ends at the putative catalytic center that is completely enclosed within the body of the protein. The putative path for RNA agrees well with biochemical data indicating that a 3' single strand overhang of 7-10 nt is necessary for binding and hydrolysis by RNase II. The presence of the clamp and the narrow channel provides an explanation for the processivity of RNase II and for why its action is limited to single-stranded RNA.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, P.O. Box 016129, Miami, FL 33101, USA.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Zuo
authors.forename: Helen A
authors.initials: HA
authors.lastname: Vincent
authors.forename: Jianwei
authors.initials: J
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Murray P
authors.initials: MP
authors.lastname: Deutscher
authors.forename: Arun
authors.initials: A
authors.lastname: Malhotra
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D005095:Exoribonucleases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D012333:RNA, Messenger; D005095:Exoribonucleases; C022535:exoribonuclease II