title: Involvement of heme regulatory motif in heme-mediated ubiquitination and degradation of IRP2.
abstract: Iron regulatory protein 2 (IRP2), a regulator of iron metabolism, is modulated by ubiquitination and degradation. We have shown that IRP2 degradation is triggered by heme-mediated oxidation. We report here that not only Cys201, an invariant residue in the heme regulatory motif (HRM), but also His204 is critical for IRP2 degradation. Spectroscopic studies revealed that Cys201 binds ferric heme, whereas His204 is a ferrous heme binding site, indicating the involvement of these residues in sensing the redox state of the heme iron and in generating the oxidative modification. Moreover, the HRM in IRP2 has been suggested to play a critical role in its recognition by the HOIL-1 ubiquitin ligase. Although HRMs are known to sense heme concentration by simply binding to heme, the HRM in IRP2 specifically contributes to its oxidative modification, its recognition by the ligase, and its sensing of iron concentration after iron is integrated into heme.
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Medicine, Osaka City University, Osaka 545-8585, Japan.
authors.forename: Haruto
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Michiko
authors.initials: M
authors.lastname: Kato
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hori
authors.forename: Koichiro
authors.initials: K
authors.lastname: Ishimori
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kirisako
authors.forename: Fuminori
authors.initials: F
authors.lastname: Tokunaga
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Iwai
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology*; D045744:Cell Line, Tumor; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000378:metabolism; D035942:Iron Regulatory Protein 2 / Q000737:chemistry / Q000378:metabolism*; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D025801:Ubiquitin; D006418:Heme; D006639:Histidine; D007501:Iron; D035942:Iron Regulatory Protein 2; D003545:Cysteine