Phosphoribulokinase activity and regulation of CO2 fixation critical for photosynthetic growth of Rhodobacter sphaeroides.
AUTOR(ES)
Hallenbeck, P L
RESUMO
The Rhodobacter sphaeroides genome contains two unlinked genetic regions each encoding numerous proteins involved in CO2 fixation which include phosphoribulokinases (prkA and prkB), ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcLS and rbcR) (P. L. Hallenbeck and S. Kaplan, Photosynth. Res. 19:63-71, 1988; F. R. Tabita, Microbiol. Rev. 52:155-189, 1988), and two open reading frames linked to rbcLS and rbcR, namely, cfxA and cfxB, respectively (P. L. Hallenbeck, R. Lerchen, P. Hessler, and S. Kaplan, J. Bacteriol. 172:1736-1748). In this study, we examined the unique role(s) of each phosphoribulokinase activity in the regulation of CO2 fixation. Strains were constructed which contain null mutations in prkA and/or prkB. Studies utilizing these strains suggested that CO2 fixation plays an essential role in attaining the cellular redox balance necessary for photoheterotrophic growth. The presence of an external electron acceptor can negate the requirement for CO2 for photoheterotrophic growth. Each form of phosphoribulokinase and ribulose 1,5-bisphosphate carboxylase/oxygenase was shown to have distinct roles in CO2 metabolism when cells were exposed to extremes in CO2 levels. Evidence is also presented which unequivocally demonstrated that regulation of the expression of the enzymes involved in CO2 metabolism is effective at the transcriptional level. Although the two regions of the DNA involved in CO2 fixation are physically unlinked, each region of the DNA can have a profound effect on the expression of the other region of the DNA.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=208665Documentos Relacionados
- Positive and negative regulation of sequences upstream of the form II cbb CO2 fixation operon of Rhodobacter sphaeroides.
- Localization and mapping of CO2 fixation genes within two gene clusters in Rhodobacter sphaeroides.
- A global signal transduction system regulates aerobic and anaerobic CO2 fixation in Rhodobacter sphaeroides.
- On the Participation of Phosphoribulokinase in the Light Regulation of CO2 Fixation 1
- Organization of phosphoribulokinase and ribulose bisphosphate carboxylase/oxygenase genes in Rhodopseudomonas (Rhodobacter) sphaeroides.