Purification and characterization of ferritin from alfalfa seeds

Ferritin from alfalfa (Medicago sativa) seeds was isolated, purified, and characterized. The apparent molecular mass of the native protein was found to be 560 kDa. Electrophoresis in denaturing gradient polyacrylamide-SDS gels revealed subunits of 28-26.5 kDa. The average iron cores were 4 nm in diameter and contained about 1400 iron atoms, with an iron-to-phosphorus ratio of 4:1. N-terminal amino acid sequencing of the 28 kDa subunit revealed close homology with other plant proteins. Immunochemical analysis using polyclonal antibodies raised against pea-seed ferritin has confirmed, in agreement with previous reports, that plant proteins share common epitopes.