Characterization of phytochelatin-like complexes from flax (Linum usitatissimum) seed

Proteins were extracted from dehulled and delipidated powder of flaxseed (cv. NorMan), and fractionated by DFAE-Sephacel anion exchange chromatography. Ultraviolet absorbance scans of ion exchange fractions eluting in buffers at pH 8.6 containing 0.45 M and 0.50 M NaCl revealed A(255) >A(280). Furthermore, the A(255) was reduced upon acidification and restored by adjusting to the original pH, confirming spectral characteristics typical of metal-thiolate complexes. Characteristic circular dichroism spectra and reversible aggregation-dissociation behavior under low and high salt conditions observed for these fractions are also typical of metal binding phytochelatins reported for other plants, while the presence of aromatic amino acids indicated by fluorescence spectra suggests some similarity to nonmetallothionein proteins. Further work is underway to investigate the prevalence of these and other complexes as well as the distribution of metals in different protein fractions of flaxseed, as a function of cultivar and geographical location.