Gene structure and expression of a novel Euglena gracilis chloroplast operon encoding cytochrome b6 and the beta and epsilon subunits of the H(+)-ATP synthase complex.
The genes encoding cytochrome b6 of the chloroplast cytochrome b6/f complex (petB) and the ATP synthase CF1-beta subunit (atpB) and epsilon-subunit (atpE) were identified on the EcoD fragment of the Euglena gracilis chloroplast genome. The complete nucleotide sequence of these three genes was determined. The petB-atpB-atpE genes are cotranscribed as a tricistronic operon. This gene organization differs from that of land plants in which atpB-atpE form a discistronic operon, and petB is within the psbB-ycf8-psbH-petB-petD operon. Euglena cytochrome b6 and the beta-subunit of the chloroplast ATP synthase are very similar in derived amino acid sequence to the corresponding gene products from other organisms. The epsilon-subunit of the chloroplast ATP synthase complex is more divergent. In Euglena, the petB-atpB-atpE genes contain introns, including two twintrons, at eight different positions. All of the intron positions were confirmed by analysis of cDNAs. Two independent intercistronic RNA processing events and 11 splicing reactions lead to the accumulation of the mature petB, atpB and atpE monocistronic mRNAs.
Hong
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Department of Biochemistry, University of Arizona, Tucson 85721.
Hallick
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002736:Chloroplasts; D003573:Cytochrome b Group / Q000096:biosynthesis / Q000235:genetics*; D045346:Cytochrome b6f Complex; D016054:DNA, Protozoan / Q000235:genetics; D004790:Enzyme Induction; D005056:Euglena gracilis / Q000235:genetics*; D005786:Gene Expression Regulation; D017343:Genes, Plant; D017125:Genes, Protozoan; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009876:Operon; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics*; D006180:Proton-Translocating ATPases / Q000096:biosynthesis / Q000235:genetics*; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D003573:Cytochrome b Group; D016054:DNA, Protozoan; D010940:Plant Proteins; D015800:Protozoan Proteins; D045346:Cytochrome b6f Complex; D006180:Proton-Translocating ATPases