title: Solution structures of DEAD-box RNA chaperones reveal conformational changes and nucleic acid tethering by a basic tail.
abstract: The mitochondrial DEAD-box proteins Mss116p of Saccharomyces cerevisiae and CYT-19 of Neurospora crassa are ATP-dependent helicases that function as general RNA chaperones. The helicase core of each protein precedes a C-terminal extension and a basic tail, whose structural role is unclear. Here we used small-angle X-ray scattering to obtain solution structures of the full-length proteins and a series of deletion mutants. We find that the two core domains have a preferred relative orientation in the open state without substrates, and we visualize the transition to a compact closed state upon binding RNA and adenosine nucleotide. An analysis of complexes with large chimeric oligonucleotides shows that the basic tails of both proteins are attached flexibly, enabling them to bind rigid duplex DNA segments extending from the core in different directions. Our results indicate that the basic tails of DEAD-box proteins contribute to RNA-chaperone activity by binding nonspecifically to large RNA substrates and flexibly tethering the core for the unwinding of neighboring duplexes.
authors: Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712, USA.
authors: Anna L
authors: AL
authors: Mallam
authors: Inga
authors: I
authors: Jarmoskaite
authors: Pilar
authors: P
authors: Tijerina
authors: Mark
authors: M
authors: Del Campo
authors: Soenke
authors: S
authors: Seifert
authors: Liang
authors: L
authors: Guo
authors: Rick
authors: R
authors: Russell
authors: Alan M
authors: AM
authors: Lambowitz
mesh_terms: D001665:Binding Sites; D002942:Circular Dichroism; D053487:DEAD-box RNA Helicases / Q000737:chemistry* / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009492:Neurospora crassa / Q000201:enzymology; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012331:RNA, Fungal / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D053838:Scattering, Small Angle; D040681:Structural Homology, Protein; D014961:X-Ray Diffraction
chemical_list: D005656:Fungal Proteins; D012331:RNA, Fungal; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C058150:MSS116 protein, S cerevisiae; D053487:DEAD-box RNA Helicases