Disease relevance of pufX

• DNA sequence analysis of the pufX region, the most distal gene of the pufBALMX operon of Rhodobacter sphaeroides, revealed a sequence encoding a putative polypeptide of 82 amino acids with a molecular mass of 9052 Da followed by a puf operon-specific transcription terminator [1].

High impact information on pufX

• It has been demonstrated before that a photosynthetically incompetent pufLMX deletion strain was not complemented by a plasmid-borne truncated puf operon version lacking only pufX, although expression of the pufL and pufM gene products was restored [2].
• The puf operon in Rhodobacter sphaeroides contains the genes for the light-harvesting antenna complex I (LHI), the reaction centre (RC) L and M subunits and an additional small open reading frame identified as pufX [2].
• We demonstrate here that the functional reinsertion of only the pufX open reading frame into the same construct is sufficient and necessary for complementation of the non-photosynthetic phenotype [2].
• Western blots using polyclonal antibodies against a synthetic peptide corresponding to a portion of the DNA-derived pufX amino acid sequence showed that the pufX open reading frame is expressed and that the gene product has an M(r) of 8-10,000 on SDS gels; a value close to the predicted mass of 9 kDa [2].
• In addition, a 120-nucleotide RNA was detected which encompassed the terminator region downstream of pufX and extended into the next downstream open reading frame [1].

Biological context of pufX

• Deletion of pufX impairs the photosynthetic generation of a transmembrane potential, suggesting a role for the PufX protein in light-driven cyclic electron transfer [Farchaus, J. W., et al. (1992) EMBO J. 11, 2779-2788] [3].
• A comparable, slowed recombination kinetics is observed in RC-LH1 complexes purified from a pufX-deleted strain [4].
• Photosynthetic deficiency of a pufX deletion mutant of Rhodobacter sphaeroides is suppressed by point mutations in the light-harvesting complex genes pufB or pufA [3].
• Complementation of a reaction center-deficient, photosynthetically incompetent pufLMX deletion strain in trans with a fragment containing the entire puf operon, including pufX and an additional 1,100 base pairs of DNA downstream of pufX, restored the reaction center and the photosynthesis-positive phenotype [5].

Other interactions of pufX

• In the puf operon no pufQ or pufX genes could be found, but the bchA gene is located upstream of that operon [6].

References