Journal Article

A Transcription Factor with a Leucine-Zipper Motif Involved in Light-Dependent Inhibition of Expression of the <i>puf</i> Operon in the Photosynthetic Bacterium <i>Rhodobacter sphaeroides</i>

Hiroshi Shimada, Tadashi Wada, Hiroshi Handa, Hiroyuki Ohta, Hiroshi Mizoguchi, Kohji Nishimura, Tatsuru Masuda, Yuzo Shioi and Ken-ichiro Takamiya

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 37, issue 4, pages 515-522
Published in print June 1996 | ISSN: 0032-0781
e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a028974
A Transcription Factor with a Leucine-Zipper Motif Involved in Light-Dependent Inhibition of Expression of the puf Operon in the Photosynthetic Bacterium Rhodobacter sphaeroides

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In the purple nonsulfur photosynthetic bacterium Rhodobacter sphaeroides the synthesis of components of the photosystem is regulated in response to oxygen tension and light intensity. We have purified and cloned a trans-acting protein (SPB) that binds to the promoter region of the puf operon, which encodes the apoproteins of light-harvesting complex I and the reaction center. The SPB was composed of a single polypeptide with an apparent molecular mass of 15.0 kDa. The nucleotide sequence of the spb gene was determined. The gene encoded 104 amino acid residues, which correspond to a molecular mass of 11.5 kDa. SPB exhibited 53% homology to HvrA in Rhodobacter capsulatus. The deduced amino acid sequence indicated that SPB contained a region with homology to the leucinezipper motif of c-JUN, a transcription factor in eukaryotes, and SPB also had a DNA-binding domain on the amino-terminal side of the leucine-zipper motif. The leucine-zipper motif of SPB might contribute to the formation of a dimer. Northern analysis indicated that spb was constitutively and monocistronically transcribed in R. sphaeroides, irrespective of growth conditions. Structural and functional differences between SPB and HvrA are discussed.

Keywords: DNA-binding protein; Leucine-zipper motif; puf operon; Rhodobacter sphaeroides; Transcription factor

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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