Identification of free fatty acids in maize protein bodies and purified α zeins by ~(13)C and ~1H nuclear magnetic resonance

摘要

Zeins, the maize storage proteins, are the most abundant proteins in the corn endosperm, and are synthesized on the rough endoplasmatic reticulum and deposited in discrete organelles called protein bodies. Several authors, using circular dichroism and optical rotatory dispersion, have concluded that these proteins have a high α-helical content in alcoholic solution. In this work we have studied these proteins, within the protein bodies themselves and after extraction from the corn grains with 70% ethanol, using NMR (nuclear magnetic resonance) spectroscopy. We conclusively demonstrate the presence of free fatty acids within both the protein bodies and also in the alcohol extracted α zeins. We present evidence for a direct interaction between the free fatty acids and the α zein proteins within the protein body and suggest possible mechanisms by which such an association has arisen during the evolution of the maize endosperm.