title: pH-dependent structures of ferritin and apoferritin in solution: disassembly and reassembly.
abstract: The pH-dependent structures of the ferritin shell (apoferritin, 24-mer) and the ferrihydrite core, under physiological conditions that permit enzymatic activity, were investigated by synchrotron small-angle X-ray scattering (SAXS). The solution structure of apoferritin was found to be nearly identical to the crystal structure. The shell thickness and hollow core volumes were estimated. The intact hollow spherical apoferritin was stable over a wide pH range, 3.40-10.0, and the ferrihydrite core was stable over the pH range 2.10-10.0. The apoferritin subunits underwent aggregation below pH 0.80, whereas the ferrihydrite cores aggregated below pH 2.10 as a result of the disassembly of the ferritin shell under the strongly acidic conditions. As the pH decreased from 3.40 to 0.80, apoferritin underwent stepwise disassembly by first forming a hollow sphere with two holes, then a headset-shaped structure, and, finally, rodlike oligomers. As the pH was increased from pH 1.96, the disassembled rodlike oligomers recovered only to the headset-shaped structure, and the disassembled headset-shaped intermediates recovered only to the hollow spherical structure with two hole defects. The apoferritin hole defects that formed during the disassembly process did not heal as the pH was increased to neutral or slightly basic conditions. The pH-induced apoferritin disassembly and reassembly processes were not fully reversible, although they were pseudoreversible over a limited pH range, between 10.0 and 2.66.
authors: Department of Chemistry, Division of Advanced Material Science, BK School of Molecular Science, Pohang University of Science and Technology, Pohang, Republic of Korea.
authors: Mihee
authors: M
authors: Kim
authors: Yecheol
authors: Y
authors: Rho
authors: Kyeong Sik
authors: KS
authors: Jin
authors: Byungcheol
authors: B
authors: Ahn
authors: Sungmin
authors: S
authors: Jung
authors: Heesoo
authors: H
authors: Kim
authors: Moonhor
authors: M
authors: Ree
mesh_terms: D001052:Apoferritins / Q000737:chemistry*; D005293:Ferritins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D012542:Scattering, Radiation; D012996:Solutions
chemical_list: D012996:Solutions; D005293:Ferritins; D001052:Apoferritins