A 4-fold axis cage mutant of ferritin L is secreted. HepG2 cells were infected with AdX-FL (wt) or the AdX-FL(L165R) cage mutant (L165R), and 72 hours after infection were labeled with ³⁵S-methionine and chased for 2 hours. Cell lysates (C) and media (M) were immunoprecipitated with polyclonal antibodies against ferritin L. In contrast to wild-type ferritin L, mutant ferritin L chains did not form high-molecular-weight oligomeric cages (arrow), but both forms are secreted.