Dataset Information

Kinetic analysis of the mitochondrial quinol-oxidizing enzymes during development of thermogenesis in Arum maculatum L.

ABSTRACT: The dependence of the rate of oxygen uptake upon the ubiquinone (Q)-pool reduction level in mitochondria isolated during the development of thermogenesis of Arum maculatum spadices has been investigated. At the alpha-stage of development, the respiratory rate was linearly dependent upon the reduction level of the Q-pool (Qr) both under state-3 and -4 conditions. Progression through the beta/gamma to the delta-stage resulted in a non-linear dependence of the state-4 rate on Qr. In the delta-stage of development, both state-3 and -4 respiratory rates were linearly dependent upon Qr due to a shift in the engagement of the alternative oxidase to lower levels of Qr. Western blot analysis revealed that increased alternative oxidase activity could be correlated with expression of a 35 kDa protein. Respiratory control was only observed with mitochondria in the alpha-stage of development. At the beta/gamma-stage of development, the addition of ADP resulted in a significant oxidation of the Q-pool which was accompanied by a decrease in the respiratory rate. This was due either to decreased contribution of the alternative pathway to the overall respiratory rate under state 3 or by deactivation of succinate dehydrogenase activity by ADP. Cold-storage of the spadices at the beta-stage of development led to increased activity of both the cytochrome pathway and succinate dehydrogenase, without any change in alternative oxidase activity. Results are discussed in terms of how changes in the activation level of the alternative oxidase and succinate dehydrogenase influence the activity and engagement of the quinol-oxidizing pathways during the development of thermogenesis in A. maculatum.

SUBMITTER: Leach GR

PROVIDER: S-EPMC1217480 | biostudies-other | 1996 Jul

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Geographical variation in abundance and composition of pollinator assemblages may result in variable selection pressures among plant populations and drive plant diversification. However, there is limited knowledge on whether differences in local visitor and pollinator assemblages are the result of site-specific strategies of plants to interact with their pollinators and/or merely reflect the pollinator availability at a given locality. To address this question, we compared locally available insect communities obtained by light-trapping with assemblages of floral visitors in populations of Arum maculatum (Araceae) from north vs. south of the Alps. We further investigated whether and how the abundance of different visitors affects plants' female reproductive success and examined the pollen loads of abundant visitors. Local insect availability explained inter-regional differences in total visitor abundance, but only partly the composition of visitor assemblages. Northern populations predominantly attracted females of Psychoda phalaenoides (Psychodidae, Diptera), reflecting the high availability of this moth fly in this region. More generalized visitor assemblages, including other psychodid and non-psychodid groups, were observed in the south, where the availability of P. phalaenoides/Psychodidae was limited. Fruit set was higher in the north than in the south but correlated positively in both regions with the abundance of total visitors and psychodids; in the north, however, this relationship disappeared when visitor abundances were too high. High pollen loads were recorded on both psychodids and other Diptera. We demonstrate for the first time that the quantitative assessment of floral visitor assemblages in relation to locally available insect communities is helpful to understand patterns of geographical variation in plant-pollinator interactions. This combined approach revealed that geographical differences in floral visitors of A. maculatum are only partly shaped by the local insect availability. Potential other factors that may contribute to the geographical pattern of visitor assemblages include the region-specific attractiveness of this plant species to flower visitors and the population-specific behavior of pollinators.

Project description:Sulfite oxidizing enzymes are essential mononuclear molybdenum (Mo) proteins involved in sulfur metabolism of animals, plants and bacteria. There are three such enzymes presently known: (1) sulfite oxidase (SO) in animals, (2) SO in plants, and (3) sulfite dehydrogenase (SDH) in bacteria. X-ray crystal structures of enzymes from all three sources (chicken SO, Arabidopsis thaliana SO, and Starkeya novella SDH) show nearly identical square pyramidal coordination around the Mo atom, even though the overall structures of the proteins and the presence of additional cofactors vary. This structural information provides a molecular basis for studying the role of specific amino acids in catalysis. Animal SO catalyzes the final step in the degradation of sulfur-containing amino acids and is critical in detoxifying excess sulfite. Human SO deficiency is a fatal genetic disorder that leads to early death, and impaired SO activity is implicated in sulfite neurotoxicity. Animal SO and bacterial SDH contain both Mo and heme domains, whereas plant SO only has the Mo domain. Intraprotein electron transfer (IET) between the Mo and Fe centers in animal SO and bacterial SDH is a key step in the catalysis, which can be studied by laser flash photolysis in the presence of deazariboflavin. IET studies on animal SO and bacterial SDH clearly demonstrate the similarities and differences between these two types of sulfite oxidizing enzymes. Conformational change is involved in the IET of animal SO, in which electrostatic interactions may play a major role in guiding the docking of the heme domain to the Mo domain prior to electron transfer. In contrast, IET measurements for SDH demonstrate that IET occurs directly through the protein medium, which is distinctly different from that in animal SO. Point mutations in human SO can result in significantly impaired IET or no IET, thus rationalizing their fatal effects. The recent developments in our understanding of sulfite oxidizing enzyme mechanisms that are driven by a combination of molecular biology, rapid kinetics, pulsed electron paramagnetic resonance (EPR), and computational techniques are the subject of this review.

Dataset Information

Kinetic analysis of the mitochondrial quinol-oxidizing enzymes during development of thermogenesis in Arum maculatum L.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets