Projected [(1)H, (15)N]-HMQC-[ (1)H, (1)H]-NOESY for large molecular systems: application to a 121 kDa protein-DNA complex.

We present a projected [(1)H,(15)N]-HMQC-[(1)H,(1)H]-NOESY experiment for observation of NOE interactions between amide protons with degenerate (15)N chemical shifts in large molecular systems. The projection is achieved by simultaneous evolution of the multiple quantum coherence of the nitrogen spin and the attached proton spin. In this way NOE signals can be separated from direct-correlation peaks also in spectra with low resolution by fully exploiting both (1)H and (15)N frequency differences, such that sensitivity can be increased by using short maximum evolution times.

Structural plasticity of peptidyl-prolyl isomerase sFkpA is a key to its chaperone function as revealed by solution NMR.

Intramolecular dynamics of periplasmic chaperone FkpA-deltaCT (sFkpA) and its complexes with partially structured substrates are studied by NMR in solution. The backbone amide 15N relaxation of sFkpA reveals flexibility in the relative orientation between the dimerization domain and two juxtaposed catalytic domains identified in the X-ray structure of sFkpA. This flexibility is attributed to the structural plasticity within the long alpha-helical arm (helix III) consisting of residues 84 and 91.