DYNAMICAL MAPPING OF ESCHERICHIA-COLI THIOREDOXIN VIA C-13 NMR RELAXATION ANALYSIS

NMR relaxation analysis was used to characterize the internal dynamics of oxidized E. coli thioredoxin in both the picosecond-nanosecond and microsecond-millisecond frequency ranges for 413 H-C and H-N bond vec tors. The C-13 relaxation data was obtained utilizing protein samples possessing an alternating C-13-C-12-C-13... labeling pattern for most enriched sites. When combined with partial deuteration, this labeling pattern provides for isolated H-1-C-13 IS spin pairs exhibiting dynami cally interpretable relaxation behavior. Side chains were found to exh ibit a far broader range of dynamics than have been previously charact erized for main chain resonances. The dynamics of structurally buried aromatic and leucine side chains are interpreted in terms of correlate d main chain-side chain torsional oscillations. Structural regions exh ibiting millisecond dynamics were found to correlate strongly with the presence of side chain-main chain or bifurcated main chain hydrogen b onds. Nuclei around the active site disulfide that exhibit mobility in the millisecond range correspond closely to the set of nuclei whose c hemical shifts are altered upon reduction. The transient conformation is interpreted in terms of enhanced reactivity due to strain at the di sulfide linkage.