Oxygen tension regulated expression of the hemA gene of Rhodobacter capsulatus
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The promoter of the Rhodobacter capsulatus hemA gene, coding for the enzyme δ-aminolevulinic acid synthase (ALAS), was identified by trans-complementation of a δ-aminolevulinic acid (ALA)-dependent mutant and found to be located within a 170 bp region proximal to the hemA gene. The activity of the hemA promoter was demonstrated by lacZ fusion and in vitro transcription-translation. An open reading frame (ORFX) was found downstream of hemA. The activity of the hemA promoter, but not that of the ORFX promoter, increased when oxygen tension was lowered in the culture. Deletions upstream of the hemA promoter region did not affect ALAS activity and formation of pigment-protein complexes in R. capsulatus.
Key wordsδ-Aminolevulinic acid synthase Bacteriochlorophyll Promoter activity Oxygen regulation Rhodobacter capsulatus
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