title: High mobility of N-terminal parts of A and B subunits of ricin.
abstract: 1H-NMR spectra (500 MHz) of ricin and its isolated A and B subunits have been analyzed in this study. It is shown that together with tight packing of the polypeptide chain there also exist flexible highly mobile segments in the structure of the proteins. Examination of the line-widths of resonances and the identification of sharp signals with protons of amino acids indicates that N-terminal peptide segments of A and B subunits are free and undergo rapid segmental motions. Spin-echo sequence (90-tau-180-tau) was used to suppress an intensive unresolved background signal from protons involved in the globular part of ricin, thus permitting selective identification of the unusually sharp signals from mobile side chains.
authors.affiliation: Institute of Experimental Cardiology, Academy of Medical Sciences, Moscow, USSR.
authors.forename: V
authors.initials: V
authors.lastname: Bushuev
authors.forename: A
authors.initials: A
authors.lastname: Tonevitsky
mesh_terms: D002367:Ricinus communis; D006609:High Mobility Group Proteins; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D010446:Peptide Fragments; D037121:Plant Lectins; D010947:Plants, Toxic; D012276:Ricin
chemical_list: D006609:High Mobility Group Proteins; D010446:Peptide Fragments; D037121:Plant Lectins; D012276:Ricin