Pervasive conformational fluctuations on microsecond time scales in a fibronectin type III domain

Abstract
A novel off-resonance rotating-frame 15N NMR spin relaxation experiment is used to characterize conformational fluctuations with correlation times between 32 and 175 μs in the third fibronectin type III domain of human tenascin-C. Conformational fluctuations of contiguous regions of the β-sandwich structure of the type III domain may represent collective motions, such as transient twisting or breathing of the β-sheets. Flexibility of the loop containing the Arg-Gly-Asp (RGD) tripeptide may affect the accessibility of this motif in protein-protein interactions.