Mesodynamics in the SARS nucleocapsid measured by NMR field cycling

Clarkson, Michael W.; Lei, Ming; Eisenmesser, Elan Z.; Labeikovsky, Wladimir; Redfield, Alfred; Kern, Dorothee

SARSN is a multifunctional protein (Surjit and Lal 2008) implicated in RNA binding (Tan et al. 2006; Zuniga et al. 2007) , capsid assembly (Hsieh et al. 2005; Saikatendu et al. 2007 ), cell-cycle disruption (Surjit et al. 2006) , and immune response to the SARS virus (Zhang et al. 2007 ). Previous experiments have indicated a flexible b-hairpin in addition to a relatively rigid antiparallel b-sheet based on the { 1 H}-15 N heteronuclear NOE at 500 MHz (Huang et al. 2004) . Sampling the spectral density over this wider range enabled us to robustly determine the time scale of motions of the hairpin and additional loops (Fig. 1) . Heteronuclear { 1 H}-15 N NOE at differing fields (50.7-91.2 MHz) were particularly useful for establishing the internal correlation times in the disordered regions. Matching internal correlation times of about 0.8 ns for many of these residues are suggestive of correlated motions, which were buttressed by molecular dynamics simulations in explicit solvent.