title: Structural characterization of the ribosomal P1A-P2B protein dimer by small-angle X-ray scattering and NMR spectroscopy.
abstract: The five ribosomal P-proteins, denoted P0-(P1-P2)2, constitute the stalk structure of the large subunit of eukaryotic ribosomes. In the yeast Saccharomyces cerevisiae, the group of P1 and P2 proteins is differentiated into subgroups that form two separate P1A-P2B and P1B-P2A heterodimers on the stalk. So far, structural studies on the P-proteins have not yielded any satisfactory information using either X-ray crystallography or NMR spectroscopy, and the structures of the ribosomal stalk and its individual constituents remain obscure. Here we outline a first, coarse-grained view of the P1A-P2B solution structure obtained by a combination of small-angle X-ray scattering and heteronuclear NMR spectroscopy. The complex has an elongated shape with a length of 10 nm and a cross section of approximately 2.5 nm. 15N NMR relaxation measurements establish that roughly 30% of the residues are present in highly flexible segments, which belong primarily to the linker region and the C-terminal part of the polypeptide chain. Secondary structure predictions and NMR chemical shift analysis, together with previous results from CD spectroscopy, indicate that the structured regions involve alpha-helices. NMR relaxation data further suggest that several helices are arranged in a nearly parallel or antiparallel topology. These results provide the first structural comparison between eukaryotic P1 and P2 proteins and the prokaryotic L12 counterpart, revealing considerable differences in their overall shapes, despite similar functional roles and similar oligomeric arrangements. These results present for the first time a view of the structure of the eukaryotic stalk constituents, which is the only domain of the eukaryotic ribosome that has escaped successful structural characterization.
authors.affiliation: Department of Molecular Biology, Institute of Microbiology and Biotechnology, Maria Curie-Skłdowska University, Akademicka 19, 20-033 Lublin, Poland.
authors.forename: Przemysłw
authors.initials: P
authors.lastname: Grela
authors.forename: Magnus
authors.initials: M
authors.lastname: Helgstrand
authors.forename: Dawid
authors.initials: D
authors.lastname: Krokowski
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Boguszewska
authors.forename: Dmitri
authors.initials: D
authors.lastname: Svergun
authors.forename: Anders
authors.initials: A
authors.lastname: Liljas
authors.forename: Pau
authors.initials: P
authors.lastname: Bernadó
authors.forename: Nikodem
authors.initials: N
authors.lastname: Grankowski
authors.forename: Mikael
authors.initials: M
authors.lastname: Akke
authors.forename: Marek
authors.initials: M
authors.lastname: Tchórzewski
mesh_terms: D000595:Amino Acid Sequence; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012269:Ribosomal Proteins / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D012542:Scattering, Radiation; D014965:X-Rays
chemical_list: C056003:RPP1A protein, S cerevisiae; C503572:RPP2B protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins