Structural domains involved in the RNA folding activity of RNA helicase II/Gu protein.
RNA helicase II/Gu (RH II/Gu) is a nucleolar protein that unwinds dsRNA in a 5' to 3' direction, and introduces a secondary structure into a ssRNA. The helicase domain is at the N-terminal three-quarters of the molecule and the foldase domain is at the C-terminal quarter. The RNA folding activity of RH II/Gu is not a mere artifact of its binding to RNA. This study narrows down the RNA foldase domain to amino acids 749-801 at the C-terminus of the protein. Dissection of this region by deletion and site-directed mutagenesis shows that the four FRGQR repeats, as well as the C-terminal end bind RNA independently. These juxtaposed subdomains are both important for the RNA foldase activity of RH II/Gu. Mutation of either repeat 2 or repeat 4, or simultaneous mutation of Lys792, Arg793 and Lys797 at the C-terminal end of RH II/Gu to alanines inhibits RNA foldase activity. The last 17 amino acids of RH II/Gu can be replaced by an RNA binding motif from nucleolar protein p120 without a deleterious effect on its foldase activity. A model is proposed to explain how RH II/Gu binds and folds an RNA substrate.
Valdez
B C
BC
Department of Pharmacology, Baylor College of Medicine, Houston, USA. bvaldez@bcm.tmc.edu
D000595:Amino Acid Sequence; D001483:Base Sequence; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020365:RNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics; D013379:Substrate Specificity
D012313:RNA; D020365:RNA Helicases