Crystal structure of human mitoNEET reveals distinct groups of iron sulfur proteins.
MitoNEET is a protein of unknown function present in the mitochondrial membrane that was recently shown to bind specifically the antidiabetic drug pioglizatone. Here, we report the crystal structure of the soluble domain (residues 32-108) of human mitoNEET at 1.8-A resolution. The structure reveals an intertwined homodimer, and each subunit was observed to bind a [2Fe-2S] cluster. The [2Fe-2S] ligation pattern of three cysteines and one histidine differs from the known pattern of four cysteines in most cases or two cysteines and two histidines as observed in Rieske proteins. The [2Fe-2S] cluster is packed in a modular structure formed by 17 consecutive residues. The cluster-binding motif is conserved in at least seven distinct groups of proteins from bacteria, archaea, and eukaryotes, which show a consensus sequence of (hb)-C-X(1)-C-X(2)-(S/T)-X(3)-P-(hb)-C-D-X(2)-H, where hb represents a hydrophobic residue; we term this a CCCH-type [2Fe-2S] binding motif. The nine conserved residues in the motif contribute to iron ligation and structure stabilization. UV-visible absorption spectra indicated that mitoNEET can exist in oxidized and reduced states. Our study suggests an electron transfer function for mitoNEET and for other proteins containing the CCCH motif.
Lin
Jinzhong
J
*National Laboratory of Biomacromolecules, Center for Structural and Molecular Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Zhou
Tao
T
Ye
Keqiong
K
Wang
Jinfeng
J
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D016384:Consensus Sequence; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D033862:Iron-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008928:Mitochondria / Q000737:chemistry*; D051336:Mitochondrial Membranes / Q000737:chemistry*; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012995:Solubility
C525595:CISD1 protein, human; D033862:Iron-Binding Proteins; D007506:Iron-Sulfur Proteins; D008024:Ligands; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D006639:Histidine; D003545:Cysteine