Studying the Signaling Role of 2-Oxoglutaric Acid Using Analogs that Mimic the Ketone and Ketal Forms of 2-Oxoglutaric Acid

College of Chemistry and Molecular Sciences, Wuhan University, 430072 Wuhan, China.
Chemistry & Biology (Impact Factor: 6.65). 09/2006; 13(8):849-56. DOI: 10.1016/j.chembiol.2006.06.009
Source: PubMed


The Silences of the Archives, the Reknown of the Story.
The Martin Guerre affair has been told many times since Jean de Coras and Guillaume Lesueur published their stories in 1561. It is in many ways a perfect intrigue with uncanny resemblance, persuasive deception and a surprizing end when the two Martin stood face to face, memory to memory, before captivated judges and a guilty feeling Bertrande de Rols. The historian wanted to go beyond the known story in order to discover the world of the heroes. This research led to disappointments and surprizes as documents were discovered concerning the environment of Artigat’s inhabitants and bearing directly on the main characters thanks to notarial contracts. Along the way, study of the works of Coras and Lesueur took a new direction. Coming back to the affair a quarter century later did not result in finding new documents (some are perhaps still buried in Spanish archives), but by going back over her tracks, the historian could only be struck by the silences of the archives that refuse to reveal their secrets and, at the same time, by the possible openings they suggest, by the intuition that almost invisible threads link here and there characters and events.

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    • "The cell-wall-related proteins can be categorized as proteins involved in (1) signal transduction , (2) synthesis, and (3) transport. Among the signal transduction proteins in Anabaena PCC 7120, histidine kinases and protein phosphatases have recently been shown to act downstream of NtcA and have been suggested to be involved in heterocyst cell wall formation (Wang et al. 2002; Cheng et al. 2006). In Anabaena PCC 7120, 131 genes encode putative histidine kinases , 52 genes code for serine/threonine and tyrosine kinases, and 13 genes code for a group of histidine and Ser/Thr hybrid (HSTKI) proteins (Ohmori et al. 2001; Phalip et al. 2001). "
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    ABSTRACT: Many multicellular cyanobacteria produce specialized nitrogen-fixing heterocysts. During diazotrophic growth of the model organism Anabaena (Nostoc) sp. strain PCC 7120, a regulated developmental pattern of single heterocysts separated by about 10 to 20 photosynthetic vegetative cells is maintained along filaments. Heterocyst structure and metabolic activity function together to accommodate the oxygen-sensitive process of nitrogen fixation. This article focuses on recent research on heterocyst development, including morphogenesis, transport of molecules between cells in a filament, differential gene expression, and pattern formation.
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    • "Heterocyst differentiation requires a number of genes involved in the different steps of the developmental process (Meeks & Elhai, 2002; Zhang et al., 2006a). At least in Anabaena 7120, heterocyst differentiation is triggered by the accumulation of 2-oxoglutarate, which acts as a signal of deprivation of combined nitrogen (Chen et al., 2006; Laurent et al., 2005; Li et al., 2003). One of the receptors of the 2-oxoglutarate signal could be NtcA, a transcription factor highly conserved in cyanobacteria (Herrero et al., 2004; Laurent et al., 2005). "
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    ABSTRACT: Heterocysts, cells specialized in N(2) fixation in cyanobacteria, appeared at near to 2.1 Ga. They constitute one of the oldest forms of differentiated cells in evolution, and are thus an interesting model for studies on evolutionary-developmental biology. How heterocysts arose during evolution remains unknown. In Anabaena PCC 7120, heterocyst development requires, among other genes, hetR for the initiation of heterocyst differentiation, and patS, encoding a diffusible inhibitor of heterocyst formation. In this study, we report that both hetR and patS are widespread among filamentous cyanobacteria that do not form heterocysts or fix N(2). hetR and patS are found in proximity on the chromosome in several cases, such as Arthrospira platensis, in which the level of HetR increased following nitrogen deprivation. The hetR gene of A. platensis could complement a hetR mutant of Anabaena PCC 7120, and patS of A. platensis could suppress heterocyst differentiation in Anabaena PCC 7120. Thus, key regulatory genes, including hetR and patS, involved in heterocyst development may have evolved before heterocysts appeared, suggesting that their function was not limited to heterocyst differentiation.
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    • "The latter conditions mimic, to some extent, nitrogen starvation in Anabaena sp. PCC 7120 (Li et al., 2003; Laurent et al., 2005; Chen et al., 2006). Interestingly, 2-OG and both its analogues also trigger Ca 2+ transients in Anabaena similar to the ones observed in S. elongatus (F. "
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    ABSTRACT: A Ca2+ signal is required for the process of heterocyst differentiation in the filamentous diazotrophic cyanobacterium Anabaena sp. PCC 7120. This paper presents evidence that a transient increase in intracellular free Ca2+ is also involved in acclimation to nitrogen starvation in the unicellular non-diazotrophic cyanobacterium Synechococcus elongatus PCC 7942. The Ca2+ transient was triggered in response to nitrogen step-down or the addition of 2-oxoglutarate (2-OG), or its analogues 2,2-difluoropentanedioic acid (DFPA) and 2-methylenepentanedioic acid (2-MPA), to cells growing with combined nitrogen, suggesting that an increase in intracellular 2-OG levels precedes the Ca2+ transient. The signalling protein P(II) and the transcriptional regulator NtcA appear to be needed to trigger the signal. Suppression of the Ca2+ transient by the intracellular Ca2+ chelator N,N'-[1,2-ethanediylbis(oxy-2,1-phenylene)]bis[N-[2-[(acetyloxy)methoxy]-2-oxoethyl]]-,bis[(acetyloxy)methyl] ester (BAPTA-AM) inhibited expression of the glnB and glnN genes, which are involved in acclimation to nitrogen starvation and transcriptionally activated by NtcA. BAPTA-AM treatment partially inhibited expression of the nblA gene, which is involved in phycobiliprotein degradation following nutrient starvation and is regulated by NtcA and NblR; in close agreement, BAPTA-AM treatment partially inhibited bleaching following nitrogen starvation. Taken together, the results presented here strongly suggest an involvement of a defined Ca2+ transient in acclimation of S. elongatus to nitrogen starvation through NtcA-dependent regulation.
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