title: Proteomic analysis and molecular modelling characterize the iron-regulatory protein haemojuvelin/repulsive guidance molecule c.
abstract: HJV (haemojuvelin) plays a key role in iron metabolism in mammals by regulating expression of the liver-derived hormone hepcidin, which controls systemic iron uptake and release. Mutations in HJV cause juvenile haemochromatosis, a rapidly progressing iron overload disorder in humans. HJV, also known as RGMc (repulsive guidance molecule c), is a member of the three-protein RGM family. RGMs are GPI (glycosylphosphatidylinositol)-linked glycoproteins that share ~50% amino acid identity and several structural motifs, including the presence of 14 cysteine residues in analogous locations. Unlike RGMa and RGMb, HJV/RGMc is composed of both single-chain and two-chain isoforms. To date there is no structural information for any member of the RGM family. In the present study we have mapped the disulfide bonds in mouse HJV/RGMc using a proteomics strategy combining sequential MS steps composed of ETD (electron transfer dissociation) and CID (collision-induced dissociation), in which ETD induces cleavage of disulfide linkages, and CID establishes disulfide bond assignments between liberated peptides. The results of the present study identified an HJV/RGMc molecular species containing four disulfide linkages. We predict using ab initio modelling that this molecule is a single-chain HJV/RGMc isoform. Our observations outline a general approach using tandem MS and ab initio molecular modelling to define unknown structural features in proteins.
authors: Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97239-3098, USA.
authors: Mahta
authors: M
authors: Nili
authors: Larry
authors: L
authors: David
authors: Johannes
authors: J
authors: Elferich
authors: Ujwal
authors: U
authors: Shinde
authors: Peter
authors: P
authors: Rotwein
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004220:Disulfides / Q000737:chemistry; D058851:GPI-Linked Proteins; D057809:HEK293 Cells; D000071020:Hemochromatosis Protein; D006801:Humans; D035925:Iron-Regulatory Proteins / Q000737:chemistry* / Q000235:genetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D040901:Proteomics / Q000379:methods*
chemical_list: D004220:Disulfides; D058851:GPI-Linked Proteins; C504414:HJV protein, mouse; D000071020:Hemochromatosis Protein; D035925:Iron-Regulatory Proteins; D008565:Membrane Proteins; D020033:Protein Isoforms