Bruno protein contains an expanded RNA recognition motif.
The RNA recognition motif (or RRM) is a ubiquitous RNA-binding module present in approximately 2% of the proteins encoded in the human genome. This work characterizes an expanded RRM, which is present in the Drosophila Bruno protein, and targets regulatory elements in the oskar mRNA through which Bruno controls translation. In this Bruno RRM, the deletion of 40 amino acids prior to the N-terminus of the canonical RRM resulted in a significantly decreased affinity of the protein for its RNA target. NMR spectroscopy showed that the expanded Bruno RRM contains the familiar RRM fold of four antiparallel beta-strands and two alpha-helices, preceded by a 10-residue loop that contacts helix alpha(1) and strand beta(2); additional amino acids at the N-terminus of the domain are relatively flexible in solution. NMR results also showed that a truncated form of the Bruno RRM, lacking the flexible N-terminal amino acids, forms a stable and complete canonical RRM, so that the loss of RNA binding activity cannot be attributed to disruption of the RRM fold. This expanded Bruno RRM provides a new example of the features that are important for RNA recognition by an RRM-containing protein.
Lyon
Angeline M
AM
Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, USA.
Reveal
Brad S
BS
Macdonald
Paul M
PM
Hoffman
David W
DW
D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D004330:Drosophila / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012313:RNA / Q000737:chemistry* / Q000235:genetics; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015027:Zebrafish
D029721:Drosophila Proteins; D016601:RNA-Binding Proteins; C093437:bru1 protein, Drosophila; C091675:osk protein, Drosophila; D012313:RNA