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Publication Abstract from PubMed

Ferritins are iron storage proteins made of 24 subunits forming a hollow spherical shell. Vertebrate ferritins contain varying ratios of heavy (H) and light (L) chains; however, known ferritin structures include only one type of chain and have octahedral symmetry. Here, we report the 1.9A structure of a secreted insect ferritin from Trichoplusia ni, which reveals equal numbers of H and L chains arranged with tetrahedral symmetry. The H/L-chain interface includes complementary features responsible for ordered assembly of the subunits. The H chain contains a ferroxidase active site resembling that of vertebrate H chains with an endogenous, bound iron atom. The L chain lacks the residues that form a putative iron core nucleation site in vertebrate L chains. Instead, a possible nucleation site is observed at the L chain 3-fold pore. The structure also reveals inter- and intrasubunit disulfide bonds, mostly in the extended N-terminal regions unique to insect ferritins. The symmetrical arrangement of H and L chains and the disulfide crosslinks reflect adaptations of insect ferritin to its role as a secreted protein.

Crystal structure of a secreted insect ferritin reveals a symmetrical arrangement of heavy and light chains.,Hamburger AE, West AP Jr, Hamburger ZA, Hamburger P, Bjorkman PJ J Mol Biol. 2005 Jun 10;349(3):558-69. Epub 2005 Apr 12. PMID:15896348^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.