Iron binding to horse spleen apoferritin: a vanadyl ENDOR spin probe study.

The role of the protein shell in the formation of the hydrous ferric oxide core of ferritin is poorly understood. A VO 2+ spin study was undertaken to characterize the initial complex of Fe 2+ with horse spleen apoferritin (96% L-subunits). A competitive binding study of VO 2+ and Fe 2+ showed that the two metals compete 1:1 for binding at the same site or region of the protein