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91.
Corynebacterial protein kinase G controls 2-oxoglutarate dehydrogenase activity via the phosphorylation status of the OdhI protein 总被引:8,自引:0,他引:8
Niebisch A Kabus A Schultz C Weil B Bott M 《The Journal of biological chemistry》2006,281(18):12300-12307
A novel regulatory mechanism for control of the ubiquitous 2-oxoglutarate dehydrogenase complex (ODH), a key enzyme of the tricarboxylic acid cycle, was discovered in the actinomycete Corynebacterium glutamicum, a close relative of important human pathogens like Corynebacterium diphtheriae and Mycobacterium tuberculosis. Based on the finding that a C. glutamicum mutant lacking serine/threonine protein kinase G (PknG) was impaired in glutamine utilization, proteome comparisons led to the identification of OdhI as a putative substrate of PknG. OdhI is a 15-kDa protein with a forkhead-associated domain and a homolog of mycobacterial GarA. By using purified proteins, PknG was shown to phosphorylate OdhI at threonine 14. The glutamine utilization defect of the delta pknG mutant could be abolished by the additional deletion of odhI, whereas transformation of a delta odhI mutant with a plasmid encoding OdhI-T14A caused a defect in glutamine utilization. Affinity purification of OdhI-T14A led to the specific copurification of OdhA, the E1 subunit of ODH. Because ODH is essential for glutamine utilization, we assumed that unphosphorylated OdhI inhibits ODH activity. In fact, OdhI was shown to strongly inhibit ODH activity with a Ki value of 2.4 nM. The regulatory mechanism described offers a molecular clue for the reduced ODH activity that is essential for the industrial production of 1.5 million tons/year of glutamate with C. glutamicum. Moreover, because this signaling cascade is likely to operate also in mycobacteria, our results suggest that the attenuated pathogenicity of mycobacteria lacking PknG might be caused by a disturbed tricarboxylic acid cycle. 相似文献
92.
Carex humilis is a clonal sedge that can form distinct rings of densely aggregated ramets. We hypothesize that rings form because both production of new ramets and ramet dispersal are positively correlated to ramet size. This would lead to an overrepresentation of fast-moving and large ramets with high ramet production at the periphery, whereas slow-moving and small ramets with low ramet production would mainly be found in the interior of rings. We use matrix models to analyse how ramet populations both at the periphery and in the interior develop in the absence of ramet dispersal. We found that the stable size class distributions of ramets predicted by the models were not different from the distributions found in the field. Also, the asymptotic ramet population growth rates (λ1) were the same. Hence, we conclude that rings would form even in the absence of a link between ramet dispersal and ramet production. Further analysis of the matrix models showed that the ramet population increases at the periphery but decreases in the interior of rings because medium and large ramets produce fewer large ramets in the interior than at the periphery. We also found that the temporal variance in λ1 and transitions rates during the four study years was much higher at the periphery than in the interior. Our results suggest that rings may form because C. humilis ramets use below-ground resources from a much larger area than the one covered by the shoots. As the clone grows larger, the soil volume available to the ramets in the interior decreases because their access to soil outside the ring is cut-off by the ramets at the periphery. Ramet density in the interior is therefore decreasing. 相似文献
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The growth of a strain of Dipodascus aggrrgatus Francke-Grosmann was strongly promoted by the aliphatic aldehyde nonanal. The highest effect was found with 80–160 μmol of nonanal per 1. The growth-promoting activity of nonanal is principally the result of an ability to shorten the lag phase. Neither the maximum value for growth nor the growth rate seem to be increased. The growth-promoting activity of nonanal could be observed only if the cells used for inoculation were taken from a culture in the phase of accelerated growth. The highest growth-promoting activity was observed when the nonanal was added before inoculation, a large effect was still observed when it was added 24 hours after inoculation, but there was no effect when it was added 33 hours after inoculation. The growth-promoting activity of nonanal remained unchanged when a mixture of 15 vitamins and growth factors was given to the medium. Nonanol and nonanoic acid stimulated growth, although to a lower degree than nonanal. There was a gradual increase in the growth-promoting effect of nonanal as the pH of the medium was increased between 3.0 and 8.0, showing that this effect is most pronounced at the higher pH values. 相似文献
98.
Summary Lysine excretion by the producer strain Corynebacterium glutamicum MH 20-22B was analyzed in relation to the internal lysine concentration. In contrast to the wild-type, lysine excretion in the producer strain was allosterically regulated by internal lysine. The apparent Hill coefficient of 1.3 – 2.2 indicates the presence of at least two cooperatively interacting lysine binding sites. 相似文献
99.
Martina Königer Brita Jessen Rui Yang Dorothea Sittler Gary C. Harris 《Photosynthesis research》2010,105(3):213-227
The goal of this study was to investigate the effects of light intensity, genotype, and various chemical treatments on chloroplast
movement in guard cells of Arabidopsis thaliana leaves. After treatment at various light intensities (dark, low, and high light), leaf discs were fixed with glutaraldehyde,
and imaged using confocal laser microscopy. Each chloroplast was assigned a horizontal (close to pore, center, or epidermal
side) and vertical (outer, middle, inner) position. White light had a distinct effect on chloroplast positioning, most notably
under high light (HL) when chloroplasts on the upper leaf surface of wild-type (WT) moved from epidermal and center positions
toward the pore. This was not the case for phot1-5/phot2-1 or phot2-1 plants, thus phototropins are essential for chloroplast positioning in guard cells. In npq1-2 mutants, fewer chloroplasts moved to the pore position under HL than in WT plants, indicating that white light can affect
chloroplast positioning also in a zeaxanthin-dependent way. Cytochalasin B inhibited the movement of chloroplasts to the pore
under HL, while oryzalin did not, supporting the idea that actin plays a role in the movement. The movement along actin cables
is dependent on CHUP1 since chloroplast positioning in chup1 was significantly altered. Abscisic acid (ABA) caused most chloroplasts in WT and phot1-5/phot2-1 to be localized in the center, middle part of the guard cells irrespective of light treatment. This indicates that not only
light but also water stress influences chloroplast positioning. 相似文献
100.
Perez-Martinez P Delgado-Lista J Garcia-Rios A Mc Monagle J Gulseth HL Ordovas JM Shaw DI Karlström B Kiec-Wilk B Blaak EE Helal O Malczewska-Malec M Defoort C Risérus U Saris WH Lovegrove JA Drevon CA Roche HM Lopez-Miranda J 《PloS one》2011,6(6):e20555
Glucokinase Regulatory Protein (GCKR) plays a central role regulating both hepatic triglyceride and glucose metabolism. Fatty acids are key metabolic regulators, which interact with genetic factors and influence glucose metabolism and other metabolic traits. Omega-3 polyunsaturated fatty acids (n-3 PUFA) have been of considerable interest, due to their potential to reduce metabolic syndrome (MetS) risk.