A base pair transition in a DNA sequence with dyad symmetry upstream of the puf promoter affects transcription of the puc operon in Rhodobacter capsulatus.
A DNA sequence with dyad symmetry upstream of the transcriptional start of the Rhodobacter capsulatus puf operon, which encodes pigment-binding proteins of the light-harvesting I complex and of the reaction center, has previously been shown to be a protein-binding site (G. Klug, Mol. Gen. Genet. 226:167-176, 1991). When a low-copy-number plasmid with a base pair transition at position -43 within this dyad symmetry in front of the puf structural genes was transferred into a Rhodobacter strain with the puf operon deleted, different phenotypes occurred during cultivation of the transconjugants and the kinetics of the loss of the wild-type phenotype was dependent on the oxygen tension in the culture. After growth for 150 generations, the different phenotypes were stably inherited. The strains having the wild-type phenotype carried the wild-type puf DNA sequence. The original mutation was still present in the strains that showed lighter color. These strains had less light-harvesting II complex in the membrane and showed lower rates of transcription of the puc operon, which encodes the proteins of this complex. This deregulation of puc expression was due to one or more chromosomally located, secondary mutations, not directly to the mutation present on the plasmid. Thus, a single-base-pair transition in the puf upstream region can result in a deregulation of puc expression, suggesting a direct or indirect transcriptional coregulation of both these operons by a common factor.
Klug
G
G
Zentrum für Molekulare Biologie, Heidelberg, Germany.
Jock
S
S
D001426:Bacterial Proteins / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial; D003227:Conjugation, Genetic; D004268:DNA-Binding Proteins / Q000235:genetics; D005784:Gene Amplification; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D009876:Operon; D010641:Phenotype; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011995:Recombination, Genetic; D016354:Rhodobacter capsulatus / Q000235:genetics*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D045322:Photosynthetic Reaction Center Complex Proteins