Assuntos
Apoproteínas/genética , Cloroplastos/metabolismo , Grupo dos Citocromos b/genética , Citocromos/genética , Genes de Plantas , Triticum/genética , Sequência de Aminoácidos , Sequência de Bases , Citocromos f , Éxons , Substâncias Macromoleculares , Dados de Sequência Molecular , Triticum/metabolismoRESUMO
The nucleotide sequence of a region of wheat chloroplast DNA containing the psbB gene for the 47 kDa chlorophyll a-binding protein of photosystem II has been determined. The gene encodes a polypeptide of 508 amino acid residues which is predicted to contain six hydrophobic membrane-spanning regions. The psbB gene is located 562 bp upstream of the psbH gene for the 10 kDa phosphoprotein of photosystem II. A small open reading frame of 38 codons is located between psbB and psbH, and on the opposite strand the psbN gene, encoding a photosystem II polypeptide of 43 amino acid residues, is located between orf38 and psbH. S1 nuclease mapping indicated that the 5' ends of transcripts were located 371 and 183 bp upstream of the psbB translation initiation codon. Predominant transcripts of 2.1 kb and 1.8 kb for psbB and 0.4 kb for psbH were present in RNA isolated from etiolated and greening wheat seedlings. Immunodecoration of Western blots indicated that the 47 kDa polypeptide was absent, or present in very low amounts, in dark-grown tissue and accumulated on greening, whereas the 10 kDa polypeptide was present in similar amounts in both dark-grown and greening seedlings. The 10 kDa polypeptide was phosphorylated in vitro by incubating wheat etioplast membranes with [gamma 32P] ATP.
Assuntos
Cloroplastos/fisiologia , Genes de Plantas , Fosfoproteínas/genética , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Triticum/genética , Sequência de Aminoácidos , Sequência de Bases , Membrana Celular/fisiologia , DNA/genética , Complexos de Proteínas Captadores de Luz , Dados de Sequência Molecular , Peso Molecular , Complexo de Proteína do Fotossistema II , Conformação Proteica , RNA/genética , RNA/isolamento & purificação , Mapeamento por Restrição , Homologia de Sequência do Ácido Nucleico , Transcrição Gênica , Triticum/fisiologiaAssuntos
Cloroplastos , Genes de Plantas , Proteínas de Choque Térmico , Triticum/genética , Proteases Dependentes de ATP , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Sequência de Bases , Cloroplastos/enzimologia , Escherichia coli/enzimologia , Escherichia coli/genética , Dados de Sequência Molecular , Fases de Leitura Aberta , Plantas/enzimologia , Plantas/genética , Homologia de Sequência do Ácido Nucleico , Serina Endopeptidases/genética , Triticum/enzimologiaRESUMO
The N-terminal amino acid sequence of a 3.2 kDa photosystem II polypeptide is shown to be identical to that of a polypeptide encoded by an open reading frame of 38 codons (orf38) in wheat chloroplast DNA. Orf38 is located just downstream of the psbE and psbF genes for the polypeptides of cytochrome b-559. Analysis of the transcription of this region of chloroplast DNA shows that psbE, psbF and orf38 are co-transcribed to give a 1.1 kb polycistronic transcript which also contains another open reading frame of 40 codons. The orf38 and orf40 products are hydrophobic polypeptides which are both predicted to span the thylakoid membrane once. Orf38 and orf40 are highly conserved, and map to similar locations adjacent to psbE and psbF, in all organisms from which this region of DNA has been sequenced. We propose that orf38 is named psbL.
