RESUMO
Recombinant clones of Schistosoma mansoni cDNA libraries containing the complete coding regions of 2 different ferritin subunits have been isolated and sequenced. This allows for the first time a comparison of ferritin sequences from an invertebrate with those of vertebrates. The deduced amino acid sequences of both Schistosoma ferritin subunit clones show significant homology to vertebrate ferritin H chains. Similarity exceeds 50% identity and includes the recently identified ferroxidase center which is present only in H chains. However, non-conservative substitutions of amino acid residues lining the 3-fold symmetry channel were found, and a gap of 3 successive amino acids unique to the 2 Schistosoma ferritin sequences was identified. Remarkably, for each of the 2 genes, we found a conspicuous difference in the amount of ferritin transcripts between females and males: one of the genes is preferentially expressed in females, the other in males.
Assuntos
Ferritinas/genética , Expressão Gênica/fisiologia , Schistosoma mansoni/genética , Homologia de Sequência do Ácido Nucleico , Sequência de Aminoácidos , Animais , Anticorpos Anti-Helmínticos , Sequência de Bases , Northern Blotting , Clonagem Molecular , Cricetinae , DNA/genética , Escherichia coli/genética , Feminino , Ferritinas/biossíntese , Biblioteca Gênica , Masculino , Dados de Sequência Molecular , RNA Mensageiro/genética , Caracteres SexuaisRESUMO
The primary structures of the nuclear-encoded 51 kDa and 78 kDa subunits of the respiratory chain NADH: ubiquinone reductase (complex I) from Neurospora crassa mitochondria were determined by sequencing cDNA and the N-terminus of the mature proteins. Both subunits are related to the soluble NAD-reducing hydrogenase of the bacterium Alcaligenes eutrophus. Sequence comparison between these subunits, the corresponding subunits of the bovine complex I and the bacterial NAD-reducing hydrogenase further confirms the binding sites of NAD(H), FMN and three iron-sulfur clusters.
Assuntos
Alcaligenes/genética , NADH Desidrogenase/genética , Neurospora crassa/genética , Quinona Redutases/genética , Alcaligenes/enzimologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação/genética , Bovinos , Mononucleotídeo de Flavina/metabolismo , Ferro/metabolismo , Mitocôndrias/enzimologia , Dados de Sequência Molecular , NAD/metabolismo , NAD(P)H Desidrogenase (Quinona) , NADH Desidrogenase/química , Neurospora crassa/enzimologia , Quinona Redutases/química , Alinhamento de Sequência , Enxofre/metabolismoRESUMO
A transferrin-binding protein (TFBP) with an apparent molecular weight of 42 kd was purified from detergent-soluble membrane proteins of bloodstream forms of Trypanosoma brucei. The protein is not expressed in the insect-borne stage of the parasite's life-cycle. Purified TFBP can be converted from an amphiphilic to a hydrophilic form by cleavage with T.brucei glycosylphosphatidylinositol (GPI)-specific phospholipase C, demonstrating that the C-terminus is modified by a GPI-membrane anchor. The TFBP is encoded by an expression-site-associated gene [ESAG 6 in the nomenclature of Pays et al. (1989) Cell, 57, 835-845] which is under the control of the promoter transcribing the expressed variant surface glycoprotein gene. The possible function of TFBP as a receptor for the uptake of transferrin in bloodstream forms is discussed.
Assuntos
Glicoproteínas/genética , Receptores da Transferrina/genética , Trypanosoma brucei brucei/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Sangue/parasitologia , Variação Genética , Glicolipídeos/farmacologia , Glicoproteínas/biossíntese , Glicosilfosfatidilinositóis , Hidrólise , Dados de Sequência Molecular , Fosfatidilinositóis/farmacologia , Regiões Promotoras Genéticas , Ratos , Trypanosoma brucei brucei/efeitos dos fármacos , Trypanosoma brucei brucei/crescimento & desenvolvimentoRESUMO
The primary structure of a nuclear-encoded subunit of the respiratory chain NADH:ubiquinone reductase (complex I) from Neurospora crassa was determined by sequencing cDNA, genomic DNA and the N-terminus of the protein. The sequence correlates to a protein of 200 amino acids and a molecular mass of 21349 Da. The protein is synthesized without a cleavable presequence. It contains two alpha-helices predicted to traverse the bilayer and is a constituent of the membrane part of complex I.
Assuntos
DNA Fúngico/genética , Neurospora crassa/genética , Quinona Redutases/genética , Sequência de Aminoácidos , Sequência de Bases , Substâncias Macromoleculares , Dados de Sequência Molecular , Peso Molecular , NAD(P)H Desidrogenase (Quinona) , Neurospora crassa/enzimologiaRESUMO
The primary structure of a 40 kDa subunit of the respiratory chain NADH:ubiquinone reductase from Neurospora crassa was determined by sequencing cDNA, genomic DNA and the N-terminus of the mature protein. The gene which is interrupted by 7 introns encodes a preprotein consisting of 375 amino acids with a 26 amino acid long presequence typical for a mitochondrial targeting signal. The sequence of the mature subunit shows conspicuous similarities to the recently [(1989) Nature 339, 147-149] discovered protein family which includes subunits I and II of the ubiquinol:cytochrome c reductase, and the processing proteins, matrix processing peptidase and processing enhancing protein, of mitochondria. The possible role of the subunit is discussed.
Assuntos
Redutases do Citocromo/genética , Endopeptidases/genética , Mitocôndrias/enzimologia , NADH Desidrogenase/genética , Sequência de Aminoácidos , DNA/genética , Íntrons , Dados de Sequência Molecular , Neurospora crassa , Mapeamento por Restrição , Homologia de Sequência do Ácido NucleicoRESUMO
The primary structure of the 49 K subunit of the respiratory chain NADH:ubiquinone reductase (complex I) from Neurospora crassa was determined by sequencing cDNA, genomic DNA and the N-terminus of the mature protein. The sequence lengths correlate to a molecular mass of 54,002 daltons for the preprotein and 49,239 daltons for the mature protein. The presequence consists of 42 amino acids of typical composition for sequences which target nuclear-encoded proteins into mitochondria. The mature protein consists of 436 amino acids and shows 64% similarity to a 49 K subunit of bovine heart NADH:ubiquinone reductase and 33% to a predicted translation product of an open reading frame in the chloroplast DNAs of Marchantia polymorpha and Nicotiana tabacum. Evidence for an iron-sulfur cluster in the subunit is discussed.
Assuntos
Neurospora crassa/genética , Quinona Redutases/genética , Sequência de Aminoácidos , Sequência de Bases , Genes Fúngicos , Dados de Sequência Molecular , NAD(P)H Desidrogenase (Quinona) , Neurospora crassa/enzimologia , Fases de Leitura Aberta , Quinona Redutases/metabolismo , Mapeamento por Restrição , Homologia de Sequência do Ácido NucleicoRESUMO
The respiratory chain NADH:ubiquinone oxidoreductase (NADH dehydrogenase or Complex I) of mitochondria comprises some 30 different subunits, and one FMN and 4 or 5 iron-sulfur clusters as internal redox groups. The bacterial glucose dehydrogenase, which oxidizes glucose to gluconolactone in the periplasmatic space and transfers the electrons to ubiquinone, is a single polypeptide chain with pyrolloquinoline quinone as the only redox group. We report here that the two different enzymes have the same ubiquinone binding domain motif and we discuss the predicted membrane folding of this domain with regard to its role in the proton translocating function of the two enzymes.
