Fpn transports zinc. HeLa cells were transfected with (A) pCMVeGFP, (B) pCMVFpn-GFP or (C) pCMVFpn162V-GFP. Twenty-four hours after transfection, cells were incubated (preloading) without or with 100μM iron (FAC) for 16 hours (-). The cells were extensively washed and incubated (loading) without (0) or with 100μM zinc at 37°C for 6 hours. Cells were washed, lysed as described in “Immunofluorescence and microscopy,” and ferritin levels determined by ELISA. The asterisks represent P values less than .05 as determined by Student t test.