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.
Related Articles 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.
Biochemistry. 1994 Mar 15;33(10):2838-42
Authors: Lycksell PO, Ingemarson R, Davis R, Gräslund A, Thelander L
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.
PMID: 8130196 [PubMed - indexed for MEDLINE]
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PubMed