title: 1H NMR studies of mouse ribonucleotide reductase: the R2 protein carboxyl-terminal tail, essential for subunit interaction, is highly flexible but becomes rigid in the presence of protein R1.
abstract: Mouse ribonucleotide reductase consists of two nonidentical subunits, proteins R1 and R2, each inactive alone. It has earlier been shown that the carboxyl-terminal part of the R2 protein is essential for subunit association to form the active enzyme complex. We now demonstrate that protein R2 gives rise to a number of sharp 1H NMR resonances, significantly narrower than the major part of the resonances. This line narrowing of certain resonances indicates segmental mobility in the molecule. In two-dimensional 1H TOCSY spectra of protein R2, cross-peak patterns from about 25 amino acid residues are visible. Most of these were assigned to the carboxyl-terminal part of the protein by comparisons with cross-peak patterns of oligopeptides corresponding to the carboxyl terminus of mouse R2 and to the patterns of a seven amino acid residue carboxyl-terminal truncated form of protein R2. These results and the magnitude of the chemical shifts of the assigned residues demonstrate that the carboxyl-terminal part of mouse R2 protein is highly mobile compared to the rest of the protein and essentially unstructured. When protein R1 is added to a solution of protein R2, the sharp resonances are broadened, suggesting that the mobility of the carboxyl-terminal tail of protein R2 is reduced. The possibility of making direct observations of subunit interaction in native and mutagenized R1/R2 proteins should allow discrimination between effects of amino acid replacements on the catalytic mechanism and effects on subunit interaction.
authors.affiliation: Department of Medical Biochemistry and Biophysics, University of Umeå, Sweden.
authors.forename: P O
authors.initials: PO
authors.lastname: Lycksell
authors.forename: R
authors.initials: R
authors.lastname: Ingemarson
authors.forename: R
authors.initials: R
authors.lastname: Davis
authors.forename: A
authors.initials: A
authors.lastname: Gräslund
authors.forename: L
authors.initials: L
authors.lastname: Thelander
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D017931:DNA Primers; D004926:Escherichia coli; D006859:Hydrogen; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051379:Mice; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D017931:DNA Primers; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D006859:Hydrogen; D012264:Ribonucleotide Reductases