CpeR is an activator required for expression of the phycoerythrin operon (cpeBA) in the cyanobacterium Fremyella diplosiphon and is encoded in the phycoerythrin linker‐polypeptide operon (cpeCDESTR)

Summary In the cyanobacteria, phycobilisomes are assembled from (αβ)6 hexamers of the coloured phycobili‐ proteins, allophycocyanin, phycocyanin and phy‐coerythrin (PE). The precise architecture of the phycobilisome is determined by the various colourless linker proteins that bind to the biliprotein...

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Published in:	Molecular microbiology Vol. 44; no. 6; pp. 1517 - 1531
Main Authors:	Cobley, John G., Clark, A. Clay, Weerasurya, Siromi, Queseda, F. Anne, Xiao, Jimmy Y., Bandrapali, Nirmala, D’Silva, Ian, Thounaojam, Maya, Oda, Jeffrey F., Sumiyoshi, Teiko, Chu, Man‐Ho
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Science Ltd 01-06-2002 Blackwell Publishing Ltd
Subjects:	Bacterial Proteins - genetics Bacterial Proteins - physiology Blotting, Northern Cloning, Molecular Cosmids Cyanobacteria - genetics Cyanobacteria - metabolism Escherichia coli - genetics Gene Expression Regulation, Bacterial - radiation effects Gene Library Light Light-Harvesting Protein Complexes Molecular Sequence Data Operon Phycobilisomes Phycoerythrin - biosynthesis Phycoerythrin - genetics Pigments, Biological - genetics Pigments, Biological - metabolism Proteins Reverse Transcriptase Polymerase Chain Reaction Transcription, Genetic
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Summary:	Summary In the cyanobacteria, phycobilisomes are assembled from (αβ)6 hexamers of the coloured phycobili‐ proteins, allophycocyanin, phycocyanin and phy‐coerythrin (PE). The precise architecture of the phycobilisome is determined by the various colourless linker proteins that bind to the biliprotein hexamers. Genes for β and α subunits of PE make up one operon (cpeBA), whereas genes for PE‐associated linker polypeptides are in a second operon. In the chromatically adapting cyanobacterium Fremyella diplosiphon green light is required for the transcription of both cpeBA and the operon encoding the PE‐associated linkers (cpeCDE). From the genome of F. diplosiphon we have identified an open reading frame, cpeR, which, when expressed from a shuttle plasmid, is capable of suppressing various mutations that cause a decrease in PE synthesis. The introduction of a shuttle plasmid bearing cpeR+ into wild‐ type F. diplosiphon caused PE expression in red light. Fremyella diplosiphon cpeR−, created by in vitro mutagenesis and in vivo homologous recombination, is fully PE and, in this strain, cpeCDE is transcribed normally whereas the transcript from cpeBA is undetectable. Polymerase chain reaction (PCR) amplification of cDNA showed that cpeR is transcribed as part of the cpeCDE operon on an extended transcript. As CpeR is an activator required for expression of the cpeBA operon, we propose that at the onset of green light the operons cpeCDESTR and cpeBA are expressed in series as a genetic cascade.
Bibliography:	Tel. (+1) 415 422 6450; Fax (+1) 415 422 5157. For correspondence. E‐mail cobley@usfca.edu ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0950-382X 1365-2958
DOI:	10.1046/j.1365-2958.2002.02966.x