An unusual organization of the genes encoding cytochrome b559 in Chlamydomonas reinhardtii: psbE and psbF genes are separately transcribed from different regions of the plastid chromosome
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- Mor, T.S., Ohad, I., Hirschberg, J. et al. Molec. Gen. Genet. (1995) 246: 600. doi:10.1007/BF00298966
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The psbE and psbF genes encode the apoproteins of cytochrome b559, an essential component of the pigment protein complex photosystem II. Together with psbL and psbJ, these genes constitute a single operon in all photosynthetic organisms examined thus far. We have cloned and sequenced the psbE and psbF genes of the Chlamydomonas reinhardtii plastid genome. The predicted amino-terminal domains of both polypeptides are more basic than those of other organisms, and the sequence of the psbE gene product indicates a departure from the ‘positive-inside’ rule for the insertion of proteins in the thylakoid membrane. Northern blot analysis demonstrated that psbE is transcribed into a 0.3 kb mRNA, while transcription of psbF and psbL genes results in a 0.9 kb transcript. The splitting of the psbEFLJ operon into separate transcription units suggests a unique mechanism of regulation of expression of these genes in C. reinhardtii.