Iron-mediated aggregation and a localized structural change characterize ferritin from a mutant light chain polypeptide that causes neurodegeneration.
J Biol Chem
; 283(46): 31679-89, 2008 Nov 14.
Article
em En
| MEDLINE
| ID: mdl-18755684
ABSTRACT
Nucleotide insertions in the ferritin light chain (FTL) polypeptide gene cause hereditary ferritinopathy, a neurodegenerative disease characterized by abnormal accumulation of ferritin and iron in the central nervous system. Here we describe for the first time the protein structure and iron storage function of the FTL mutant p.Phe167SerfsX26 (MT-FTL), which has a C terminus altered in sequence and extended in length. MT-FTL polypeptides assembled spontaneously into soluble, spherical 24-mers that were ultrastructurally indistinguishable from those of the wild type. Far-UV CD showed a decrease in alpha-helical content, and 8-anilino-1-naphthalenesulfonate fluorescence revealed the appearance of hydrophobic binding sites. Near-UV CD and proteolysis studies suggested little or no structural alteration outside of the C-terminal region. In contrast to wild type, MT-FTL homopolymers precipitated at much lower iron loading, had a diminished capacity to incorporate iron, and were less thermostable. However, precipitation was significantly reversed by addition of iron chelators both in vitro and in vivo. Our results reveal substantial protein conformational changes localized at the 4-fold pore of MT-FTL homopolymers and imply that the C terminus of the MT-FTL polypeptide plays an important role in ferritin solubility, stability, and iron management. We propose that the protrusion of some portion of the C terminus above the spherical shell allows it to cross-link with other mutant polypeptides through iron bridging, leading to enhanced mutant precipitation by iron. Our data suggest that hereditary ferritinopathy pathogenesis is likely to result from a combination of reduction in iron storage function and enhanced toxicity associated with iron-induced ferritin aggregates.
Texto completo:
1
Coleções:
01-internacional
Temas:
Geral
/
Agentes_cancerigenos
Base de dados:
MEDLINE
Assunto principal:
Peptídeos
/
Ferritinas
/
Ferro
/
Degeneração Neural
Tipo de estudo:
Etiology_studies
Limite:
Animals
/
Humans
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
2008
Tipo de documento:
Article
País de afiliação:
Estados Unidos