A leucine zipper protein of mitochondrial origin.
Sequence-specific DNA-binding proteins are characterised by short coiled-coil structural domains classified as zinc finger/RING finger, leucine zipper (L-Zip) or helix-loop-helix (HLH) motifs. The L-Zip proteins are defined by a pattern of at least four leucine (L) residues repeated every seventh amino acid that mediates protein dimerisation through the formation of parallel alpha-helical dimers. Usually the zipper is incorporated into a helix-loop-helix conformation called the basic helix-loop-helix-leucine zipper (bHLH/Zip). To date, all of the several hundred proteins reported as containing the L-Zip and/or bHLH/Zip motifs are nuclear-encoded. No leucine zipper polypeptide has, hitherto, been reported as mitochondrial in origin. Here we report such a polypeptide, the nicotinamide dehydrogenase subunit 4L (nad4L). We first identified this in human blood flukes of the genus Schistosoma (phylum Platyhelminthes; class Trematoda) but show that this is a common feature in other eucaryotes as well. Therefore, in addition to their well recognised role in oxidative phosphorylation, nad4L proteins may be pivotally involved in a range of other biological processes such as transcription and/or replication activation or as signal transmitters in communication with the nucleus and other cellular organelles. This may indicate a link between transcription regulation and respiration in mitochondria. We have also identified L-Zip-like motifs in nuoK, the procaryotic equivalent of the nad4L mitochondrial protein.
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Molecular Parasitology Unit, Australian Centre for International and Tropical Health and Nutrition, Queensland Institute of Medical Research and University of Queensland, 300 Herston Road, Brisbaner, Qld 4029, Australia.
Blair
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McManus
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D000595:Amino Acid Sequence; D000818:Animals; D019069:Cell Respiration / Q000235:genetics; D017124:Conserved Sequence; D016208:Databases, Factual; D042967:Electron Transport Complex I; D005057:Eukaryotic Cells / Q000201:enzymology; D005786:Gene Expression Regulation; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D006801:Humans; D016350:Leucine Zippers / Q000235:genetics*; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000235:genetics*; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid
D021122:Protein Subunits; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I