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Regulation of CO2 Concentrating Mechanism in Cyanobacteria.

Burnap RL, Hagemann M, Kaplan A - Life (Basel) (2015)

Bottom Line: The structural components for several of the transport and uptake mechanisms are described and the progress towards elucidating their regulation is discussed in the context of studies, which have documented metabolomic changes in response to changes in Ci availability.Genes for several of the transport and uptake mechanisms are regulated by transcriptional regulators that are in the LysR-transcriptional regulator family and are known to act in concert with small molecule effectors, which appear to be well-known metabolites.Finally, emerging evidence for an additional layer of regulatory complexity involving small non-coding RNAs is discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, Henry Bellmon Research Center, Oklahoma State University, Stillwater, OK 74078, USA. rob.burnap@okstate.edu.

ABSTRACT
In this chapter, we mainly focus on the acclimation of cyanobacteria to the changing ambient CO2 and discuss mechanisms of inorganic carbon (Ci) uptake, photorespiration, and the regulation among the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. The structural components for several of the transport and uptake mechanisms are described and the progress towards elucidating their regulation is discussed in the context of studies, which have documented metabolomic changes in response to changes in Ci availability. Genes for several of the transport and uptake mechanisms are regulated by transcriptional regulators that are in the LysR-transcriptional regulator family and are known to act in concert with small molecule effectors, which appear to be well-known metabolites. Signals that trigger changes in gene expression and enzyme activity correspond to specific "regulatory metabolites" whose concentrations depend on the ambient Ci availability. Finally, emerging evidence for an additional layer of regulatory complexity involving small non-coding RNAs is discussed.

No MeSH data available.


Overview of the different regulatory levels adjusting the activity of the CO2 concentrating mechanism (CCM) according to the ambient inorganic carbon levels.
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life-05-00348-f002: Overview of the different regulatory levels adjusting the activity of the CO2 concentrating mechanism (CCM) according to the ambient inorganic carbon levels.

Mentions: The activity of the CCM is strongly affected by the concentration of CO2 experienced by the cells during growth. Indeed, the regulation of the CCM is a striking example of how cells may produce changes in physiological state in response to a single environmental parameter. Cyanobacteria grown under elevated CO2 concentrations exhibit a relatively lower apparent whole cell photosynthetic affinity for extracellular Ci (Ks ~200 μM) compared to cells adapted to low availability of CO2 (Ks ~10 μM) [10,53]. These are aggregate, whole cell affinities that reflect the changes in the abundance and kinetic characteristics of multiple transporters and CO2 uptake enzymes. Moreover, there is considerable phyletic variation in the actual composition and expression of these different Ci-uptake “subsystems”, which is only gradually becoming apparent with advances in genomics [34]. Finally, the details of the regulatory mechanisms controlling the interchange between the low affinity state and the high affinity states are only beginning to emerge, but it is clear that regulation is exerted at multiple levels. As discussed below, regulation involves gene expression, with both transcriptional and post-transcriptional components, as well as modulation of the activity of the expressed transporters. Understanding the signals triggering these changes is also becoming better understood. It now appears that internal metabolic changes that occur in response to changing Ci availability are at the heart of this regulation. Accordingly, the signals that trigger changes in gene expression and enzyme activity correspond to specific “regulatory metabolites” whose concentrations predictably depend upon the ambient Ci availability (Figure 2). Therefore, an understanding of the regulation of the CCM appears to require both the detailed information about metabolic fluctuations, on the one hand, and the allosteric interactions between regulatory proteins and their cognate metabolic effector molecules, on the other.


Regulation of CO2 Concentrating Mechanism in Cyanobacteria.

Burnap RL, Hagemann M, Kaplan A - Life (Basel) (2015)

Overview of the different regulatory levels adjusting the activity of the CO2 concentrating mechanism (CCM) according to the ambient inorganic carbon levels.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390856&req=5

life-05-00348-f002: Overview of the different regulatory levels adjusting the activity of the CO2 concentrating mechanism (CCM) according to the ambient inorganic carbon levels.
Mentions: The activity of the CCM is strongly affected by the concentration of CO2 experienced by the cells during growth. Indeed, the regulation of the CCM is a striking example of how cells may produce changes in physiological state in response to a single environmental parameter. Cyanobacteria grown under elevated CO2 concentrations exhibit a relatively lower apparent whole cell photosynthetic affinity for extracellular Ci (Ks ~200 μM) compared to cells adapted to low availability of CO2 (Ks ~10 μM) [10,53]. These are aggregate, whole cell affinities that reflect the changes in the abundance and kinetic characteristics of multiple transporters and CO2 uptake enzymes. Moreover, there is considerable phyletic variation in the actual composition and expression of these different Ci-uptake “subsystems”, which is only gradually becoming apparent with advances in genomics [34]. Finally, the details of the regulatory mechanisms controlling the interchange between the low affinity state and the high affinity states are only beginning to emerge, but it is clear that regulation is exerted at multiple levels. As discussed below, regulation involves gene expression, with both transcriptional and post-transcriptional components, as well as modulation of the activity of the expressed transporters. Understanding the signals triggering these changes is also becoming better understood. It now appears that internal metabolic changes that occur in response to changing Ci availability are at the heart of this regulation. Accordingly, the signals that trigger changes in gene expression and enzyme activity correspond to specific “regulatory metabolites” whose concentrations predictably depend upon the ambient Ci availability (Figure 2). Therefore, an understanding of the regulation of the CCM appears to require both the detailed information about metabolic fluctuations, on the one hand, and the allosteric interactions between regulatory proteins and their cognate metabolic effector molecules, on the other.

Bottom Line: The structural components for several of the transport and uptake mechanisms are described and the progress towards elucidating their regulation is discussed in the context of studies, which have documented metabolomic changes in response to changes in Ci availability.Genes for several of the transport and uptake mechanisms are regulated by transcriptional regulators that are in the LysR-transcriptional regulator family and are known to act in concert with small molecule effectors, which appear to be well-known metabolites.Finally, emerging evidence for an additional layer of regulatory complexity involving small non-coding RNAs is discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, Henry Bellmon Research Center, Oklahoma State University, Stillwater, OK 74078, USA. rob.burnap@okstate.edu.

ABSTRACT
In this chapter, we mainly focus on the acclimation of cyanobacteria to the changing ambient CO2 and discuss mechanisms of inorganic carbon (Ci) uptake, photorespiration, and the regulation among the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. The structural components for several of the transport and uptake mechanisms are described and the progress towards elucidating their regulation is discussed in the context of studies, which have documented metabolomic changes in response to changes in Ci availability. Genes for several of the transport and uptake mechanisms are regulated by transcriptional regulators that are in the LysR-transcriptional regulator family and are known to act in concert with small molecule effectors, which appear to be well-known metabolites. Signals that trigger changes in gene expression and enzyme activity correspond to specific "regulatory metabolites" whose concentrations depend on the ambient Ci availability. Finally, emerging evidence for an additional layer of regulatory complexity involving small non-coding RNAs is discussed.

No MeSH data available.