THE EMBRYO-SPECIFIC EMB-1 PROTEIN OF DAUCUS-CAROTA IS FLEXIBLE AND UNSTRUCTURED IN SOLUTION

The EMB-1 protein is a highly hydrophilic protein of unknown function that accumulates in embryos of carrot before seed desiccation. To inve stigate the structure of this protein, it was expressed in E. coli, an d purified to near homogeneity by Q-Sepharose anion exchange chromatog raphy and ultrafiltration. The purified protein was characterized by H -1 nuclear magnetic resonance (NMR) spectroscopy under both aqueous co nditions and conditions simulating desiccation, The NMR results reveal poor chemical shift dispersion, rapid chemical exchange of the amide backbone protons, unexpectedly narrow linewidths and the general absen ce of nuclear Overhauser effects. Together, these results indicate the EMB-1 protein has no defined secondary or tertiary structure in solut ion and the polypeptide backbone of the EMB-1 protein is flexible on a sub-nanosecond time scale.