Magic angle spinning NMR spectroscopy of thioredoxin reassemblies

Differentially isotopically enriched 1–73(13C,15N)/74–108(15N) and 1–73(15N)/74–108(13C,15N) Escherichia coli thioredoxin reassemblies prepared by fragment complementation were investigated by high-resolution magic angle spinning solid-state NMR spectroscopy. Nearly complete resonance assignments, secondary and tertiary structure analysis are reported for 1–73(13C,15N)/74–108(15N) reassembled thioredoxin. Temperature dependence of the dipolar-assisted rotational resonance (DARR) spectra reveals the residues undergoing intermediate timescale motions at temperatures below − 15 °C. Analysis of the DARR intensity buildups as a function of mixing time in these reassemblies indicates that at long mixing times medium- and long-range cross-peaks do not experience dipolar truncation, suggesting that isotopic dilution is not required for gaining nontrivial distance restraints for structure calculations. Copyright © 2007 John Wiley & Sons, Ltd.