title: Quaternary arrangement of an active, native group II intron ribonucleoprotein complex revealed by small-angle X-ray scattering.
abstract: The stable ribonucleoprotein (RNP) complex formed between the Lactococcus lactis group II intron and its self-encoded LtrA protein is essential for the intron's genetic mobility. In this study, we report the biochemical, compositional, hydrodynamic and structural properties of active group II intron RNP particles (+A) isolated from its native host using a novel purification scheme. We employed small-angle X-ray scattering to determine the structural properties of these particles as they exist in solution. Using sucrose as a contrasting agent, we derived a two-phase quaternary model of the protein-RNA complex. This approach revealed that the spatial properties of the complex are largely defined by the RNA component, with the protein dimer located near the center of mass. A transfer RNA fusion engineered into domain II of the intron provided a distinct landmark consistent with this interpretation. Comparison of the derived +A RNP shape with that of the previously reported precursor intron (ΔA) particle extends previous findings that the loosely packed precursor RNP undergoes a dramatic conformational change as it compacts into its active form. Our results provide insights into the quaternary arrangement of these RNP complexes in solution, an important step to understanding the transition of the group II intron from the precursor to a species fully active for DNA invasion.
authors.affiliation: Department of Biochemistry & Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6059, USA, Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712, USA, Wadsworth Center, NYS Department of Health, Albany, NY 12201, USA, Department of Biological Sciences and RNA Institute, University at Albany, State University of New York, Albany, NY 12222, USA, SUNY Downstate Medical Center, University Hospital, Brooklyn, NY 11203, USA and Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA.
authors.forename: Kushol
authors.initials: K
authors.lastname: Gupta
authors.forename: Lydia M
authors.initials: LM
authors.lastname: Contreras
authors.forename: Dorie
authors.initials: D
authors.lastname: Smith
authors.forename: Guosheng
authors.initials: G
authors.lastname: Qu
authors.forename: Tao
authors.initials: T
authors.lastname: Huang
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Spruce
authors.forename: Steven H
authors.initials: SH
authors.lastname: Seeholzer
authors.forename: Marlene
authors.initials: M
authors.lastname: Belfort
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Van Duyne
mesh_terms: D007438:Introns; D013294:Lactococcus lactis / Q000235:genetics; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D055503:Protein Multimerization; D012343:RNA, Transfer / Q000737:chemistry; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D012261:Ribonucleoproteins; D012343:RNA, Transfer