title: Sm-like proteins in Eubacteria: the crystal structure of the Hfq protein from Escherichia coli.
abstract: The Hfq protein was discovered in Escherichia coli in the early seventies as a host factor for the Qbeta phage RNA replication. During the last decade, it was shown to be involved in many RNA processing events and remote sequence homology indicated a link to spliceosomal Sm proteins. We report the crystal structure of the E.coli Hfq protein showing that its monomer displays a characteristic Sm-fold and forms a homo-hexamer, in agreement with former biochemical data. Overall, the structure of the E.coli Hfq ring is similar to the one recently described for Staphylococcus aureus. This confirms that bacteria contain a hexameric Sm-like protein which is likely to be an ancient and less specialized form characterized by a relaxed RNA binding specificity. In addition, we identified an Hfq ortholog in the archaeon Methanococcus jannaschii which lacks a classical Sm/Lsm gene. Finally, a detailed structural comparison shows that the Sm-fold is remarkably well conserved in bacteria, Archaea and Eukarya, and represents a universal and modular building unit for oligomeric RNA binding proteins.
authors.affiliation: European Molecular Biology Laboratory, Structural and Computational Biology Programme, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
authors.forename: Claude
authors.initials: C
authors.lastname: Sauter
authors.forename: Jérôme
authors.initials: J
authors.lastname: Basquin
authors.forename: Dietrich
authors.initials: D
authors.lastname: Suck
mesh_terms: D000595:Amino Acid Sequence; D001324:Autoantigens; D001419:Bacteria / Q000235:genetics*; D018360:Crystallography, X-Ray; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics*; D019143:Evolution, Molecular; D035001:Host Factor 1 Protein / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017411:Ribonucleoproteins, Small Nuclear / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D055517:snRNP Core Proteins
chemical_list: D001324:Autoantigens; D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins