TAILIEUCHUNG - Báo cáo khoa học: Cyanobacteria contain a structural homologue of the Hfq protein with altered RNA-binding properties

Hfq proteins are common in many species of enterobacteria, where they participate in RNA folding and translational regulation through pairing of small RNAs and messenger RNAs. Hfq proteins share the distinctive Sm fold, and form ring-shaped structures similar to those of the Sm⁄Lsm pro-teins regulating mRNA turnover in eukaryotes. | ễFEBS Journal Cyanobacteria contain a structural homologue of the Hfq protein with altered RNA-binding properties Andreas B0ggild1 2 Martin Overgaard1 3 Poul Valentin-Hansen1 3 and Ditlev E. Brodersen1 2 1 Centre for mRNP Biogenesis and Metabolism University of Aarhus Denmark 2 Department of Molecular Biology University of Aarhus Denmark 3 Department of Biochemistry and Molecular Biology University of Southern Denmark Odense M Denmark Keywords cyanobacteria Hfq RNA-binding protein Sm translationalregulation Correspondence D. E. Brodersen University of Aarhus Denmark Gustav Wieds Vej10c DK-8000 Aarhus C Denmark Fax 45 8612 3178 Tel 45 8942 5259 E-mail deb@ Website http deb Database Structure models and diffraction data are available in the Protein Data Bank under the accession numbers 3HFO Syn-Hfq and 3HFN Ana-Hfq Received 3 March 2009 revised 23 April 2009 accepted 19 May 2009 doi Hfq proteins are common in many species of enterobacteria where they participate in RNA folding and translational regulation through pairing of small RNAs and messenger RNAs. Hfq proteins share the distinctive Sm fold and form ring-shaped structures similar to those of the Sm Lsm proteins regulating mRNA turnover in eukaryotes. However bacterial Hfq proteins are homohexameric whereas eukaryotic Sm Lsm proteins are heteroheptameric. Recently Hfq proteins with poor sequence conservation were identified in archaea and cyanobacteria. In this article we describe crystal structures of the Hfq proteins from the cyanobacteria Synechocystis sp. PCC 6803 and Anabaena PCC 7120 at and A resolution respectively and show that they retain the classic Sm fold despite low sequence conservation. In addition the intersubunit contacts and RNA-binding site are divergent and we show biochemically that the proteins bind very weakly to known Escherichia coli Hfq target RNAs in vitro. Moreover when expressed in E. coli the proteins cannot mediate

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