LAUSR

Description of protein dynamics is known to be essential in understanding their function. Studies based on a well established $$^{15}\hbox {N}$$15N NMR relaxation methodology have been applied to a large number of systems. However, the low dispersion of $$^{1}\hbox {H}$$1H chemical shifts very often observed within intrinsically disordered proteins complicates utilization of standard 2D HN correlated spectra because a limited number of amino acids can be characterized. Here we present a suite of triple resonance HNCO-type NMR experiments for measurements of five $$^{15}\hbox {N}$$15N relaxation parameters ($$R_1$$R1, $$R_2$$R2, NOE, cross-correlated relaxation rates $$\Gamma _x$$Γx and $$\Gamma _z$$Γz) in doubly $$^{13}\hbox {C}$$13C,$$^{15}\hbox {N}$$15N-labeled proteins. We show that the third spectral dimension combined with non-uniform sampling provides relaxation rates for almost all residues of a protein with extremely poor chemical shift dispersion, the C terminal domain of $$\delta$$δ-subunit of RNA polymerase from Bacillus subtilis. Comparison with data obtained using a sample labeled by $$^{15}\hbox {N}$$15N only showed that the presence of $$^{13}\hbox {C}$$13C has a negligible effect on $$\Gamma _x$$Γx, $$\Gamma _z$$Γz, and on the cross-relaxation rate (calculated from NOE and $$R_1$$R1), and that these relaxation rates can be used to calculate accurate spectral density values. Partially $$^{13}\hbox {C}$$13C-labeled sample was used to test if the observed increase of $$^{15}\hbox {N}$$15N$$R_1$$R1 in the presence of $$^{13}\hbox {C}$$13C corresponds to the $$^{15}\hbox {N}-^{13}\hbox {C}$$15N-13C dipole–dipole interactions in the $$^{13}\hbox {C}$$13C,$$^{15}\hbox {N}$$15N-labeled sample.