Backbone dynamics of the oligomerization domain of p53 determined from 15N NMR relaxation measurements

Abstract

The backbone dynamics of the tetrameric p53 oligomerization domain (residues 319–360) have been investigated by two‐dimensional inverse detected heteronuclear 1 H‐15 N NMR spectroscopy at 500 and 600 MHz. 15 N T 1, T 2, and heteronuclear NOEs were measured for 39 of 40 non‐proline backbone NH vectors at both field strengths. The overall correlation time for the tetramer, calculated from the T 1/T 2 ratios, was found to be 14.8 ns at 35 °C. The correlation times and amplitudes of the internal motions were extracted from the relaxation data using the model‐free formalism (Lipari G, Szabo A, 1982, J Am Chem Soc 104:4546–4559). The internal dynamics of the structural core of the p53 oligomerization domain are uniform and fairly rigid, with residues 327–354 exhibiting an average generalized order parameter (S 2) of 0.88 ± 0.08. The N‐ and C‐termini exhibit substantial mobility and are unstructured in the solution structure of p53. Residues located at the N‐ and C‐termini, in the β‐sheet, in the turn between the α‐helix and β‐sheet, and at the C‐terminal end of the α‐helix display two distinct internal motions that are faster than the overall correlation time. Fast internal motions (±20 ps) are within the extreme narrowing limit and are of uniform amplitude. The slower motions (0.6–2.2 ns) are outside the extreme narrowing limit and vary in amplitude. Four residues at the tetramer interface exhibit a small degree of conformational averaging as evidenced by 15 N line broadening, possibly due to sliding or rolling of the helices at the interface of the two dimers that form the tetramer.