The prevalence of
food allergy has increased in recent years, and Korean pine
vicilin is a potential food
allergen. We have previously reported the crystallization of Korean pine
vicilin purified from raw pine nut. Here we report the isolation of
vicilin mRNA and the crystal structure of Korean pine
vicilin at 2.40 Å resolution. The overall structure of pine nut
vicilin is similar to the structures of other 7S
seed storage proteins and consists of an N-terminal domain and a C-terminal domain. Each assumes a cupin fold, and they are symmetrically related about a pseudodyad axis. Three
vicilin molecules form a doughnut-shaped trimer through head-to-tail association. Structure characterization of Korean pine nut
vicilin unexpectedly showed that, in its native trimeric state, the
vicilin has three
copper ligands. Sequence alignments suggested that the
copper-coordinating residues were conserved in winter squash, sesame, tomato, and several tree nuts, while they were not conserved in a number of legumes, including peanut and soybean. Additional studies are needed to assess whether the
copper-coordinating property of vicilins has a
biological function in the relevant plants. The nutritional value of this
copper-coordinating
protein in tree nuts and other edible seeds may be worth further investigations.