Cytochrome c550 in the cyanobacterium Thermosynechococcus elongatus: Study of redox mutants

Cytochrome c550 is one of the extrinsic Photosystem II subunits in cyanobacteria and red algae. To study the possible role of the heme of the cytochrome c550 we constructed two mutants of Thermosynechococcus elongatus in which the residue His-92, the sixth ligand of the heme, was replaced by a Met or a Cys in order to modify the redox properties of the heme. The H92M and H92C mutations changed the midpoint redox potential of the heme in the isolated cytochrome by +125 mV and –30 mV, respectively, compared with the wild type. The binding-induced increase of the redox potential observed in the wild type and the H92C mutant was absent in the H92M mutant. Both modified cytochromes were more easily detachable from the Photosystem II compared with the wild type. The Photosystem II activity in cells was not modified by the mutations suggesting that the redox potential of the cytochrome c550 is not important for Photosystem II activity under normal growth conditions. A mutant lacking the cytochrome c550 was also constructed. It showed a lowered affinity for Cl– and Ca2+ as reported earlier for the cytochrome c550-less Synechocystis 6803 mutant, but it showed a shorter lived Formula state, rather than a stabilized S2 state and rapid deactivation of the enzyme in the dark, which were characteristic of the Synechocystis mutant. It is suggested that the latter effects may be caused by loss (or weaker binding) of the other extrinsic proteins rather than a direct effect of the absence of the cytochrome c55

Simultaneous Determination of Various Isothiocyanates by RP-LC Following Precolumn Derivatization with Mercaptoethanol

Numerous isothiocyanates (ITCs) are poorly soluble in water which causes their precipitation in aqueous mobile phases used in reversed phase liquid chromatography (RP-LC), thus impacting the accuracy of the quantification. By comparing the amounts of ITCs injected and released from the column, losses could be estimated at 5–32% depending on polarities and concentrations. Results could be dramatically improved in terms of separation and quantification using RP-LC with a mercaptoethanol precolumn derivatization aimed at avoiding ITCs precipitation. The cancer chemoprotective allyl-ITC and sulforaphane were found in cabbage extracts at 1.2 and 2.7 μg g−1 fresh weight, respectively

Research of functional and technological interest isothiocyanates in Brassicaceae

Les isothiocyanates (ITCs), produits de dégradation des glucosinolates, sont des molécules présentes dans diverses familles végétales dont les Brassicacées. Des travaux de recherche ont suggéré que les ITCs ont des effets bénéfiques sur la santé, notamment en empêchant la prolifération des cellules cancéreuses et qu ils possèdent des propriétés antimicrobiennes pouvant être exploitées dans les procédés industriels. Cependant, les données concernant les propriétés biologiques des ITCs, ainsi que les mécanismes moléculaires auxquels ils participent restent encore souvent inexpliqués. L'objectif de ce travail a été de mettre au point des méthodes permettant une analyse qualitative et quantitative d'ITCs ayant des structures physico-chimiques différentes. Les méthodes ont ensuite été appliquées à l'analyse du contenu en ITC de végétaux produits en Alsace. Les résultats obtenus ont permis de mettre en évidence une diversité qualitative et quantitative du contenu en ITC en fonction de l'espèce et de la variété de Brassicacées. En parallèle, des tests d'activité antibactérienne et anticancéreuse ont été réalisés afin de sélectionner les espèces moléculaires les plus efficaces. Pour l'activité antibactérienne, il s'est avéré que l'efficacité d'inhibition des cellules bactériennes dépendait á la fois de l'espèce bactérienne, de la structure chimique de la chaine latérale des ITCs et de leur concentration. Quant à l'étude de l'activité anticancéreuse, les résultats ont montré que les ITCs sont capable d'inhiber des cellules cancéreuses coliques.The isothiocyanates (ITCs), breakdown products of the glucosinolates, are molecules present in various vegetable families such as Brassicaceae. Research suggested that ITCs have beneficial effects on health; particularly by preventing the proliferation of cancer cells and that they have antibacterial properties being able to be exploited in industrial processes. However, data concerning the biological properties of ITCs, as well as the molecular mechanisms in which they take part remain still often unexplained. The objective of this work was to develop methods allowing a qualitative and quantitative analysis of ITCs with various physicochemical properties. These methods were then applied to analyze the ITC contents in plants produced in Alsace. Our results highlighted a qualitative and quantitative diversity of the ITC contents, depending on the species and on the variety of Brassicaceae. Indeed; antibacterial and anticancer activity tests were carried out in order to select the most effective molecular species. Antibacterial activity test showed that the effectiveness of ITCs on bacterial cells inhibition was related to bacterial species itself and the chemical structure of the side chain of ITCs as well as their concentration. Anti-cancer activity tests showed that ITCs are able to inhibit colon cancer cells

Research of functional and technological interest isothiocyanates in Brassicaceae

Les isothiocyanates (ITCs), produits de dégradation des glucosinolates, sont des molécules présentes dans diverses familles végétales dont les Brassicacées. Des travaux de recherche ont suggéré que les ITCs ont des effets bénéfiques sur la santé, notammenThe isothiocyanates (ITCs), breakdown products of the glucosinolates, are molecules present in various vegetable families such as Brassicaceae. Research suggested that ITCs have beneficial effects on health; particularly by preventing the proliferation o

Recherche d'isothiocyanates à intérêts fonctionnel et technologique chez les Brassicacées

Les isothiocyanates (ITCs), produits de dégradation des glucosinolates, sont des molécules présentes dans diverses familles végétales dont les Brassicacées. Des travaux de recherche ont suggéré que les ITCs ont des effets bénéfiques sur la santé, notamment en empêchant la prolifération des cellules cancéreuses et qu ils possèdent des propriétés antimicrobiennes pouvant être exploitées dans les procédés industriels. Cependant, les données concernant les propriétés biologiques des ITCs, ainsi que les mécanismes moléculaires auxquels ils participent restent encore souvent inexpliqués. L objectif de ce travail a été de mettre au point des méthodes permettant une analyse qualitative et quantitative d ITCs ayant des structures physico-chimiques différentes. Les méthodes ont ensuite été appliquées à l analyse du contenu en ITC de végétaux produits en Alsace. Les résultats obtenus ont permis de mettre en évidence une diversité qualitative et quantitative du contenu en ITC en fonction de l espèce et de la variété de Brassicacées. En parallèle, des tests d activité antibactérienne et anticancéreuse ont été réalisés afin de sélectionner les espèces moléculaires les plus efficaces. Pour l activité antibactérienne, il s est avéré que l efficacité d inhibition des cellules bactériennes dépendait á la fois de l espèce bactérienne, de la structure chimique de la chaine latérale des ITCs et de leur concentration. Quant à l étude de l activité anticancéreuse, les résultats ont montré que les ITCs sont capable d inhiber des cellules cancéreuses coliques.The isothiocyanates (ITCs), breakdown products of the glucosinolates, are molecules present in various vegetable families such as Brassicaceae. Research suggested that ITCs have beneficial effects on health; particularly by preventing the proliferation of cancer cells and that they have antibacterial properties being able to be exploited in industrial processes. However, data concerning the biological properties of ITCs, as well as the molecular mechanisms in which they take part remain still often unexplained. The objective of this work was to develop methods allowing a qualitative and quantitative analysis of ITCs with various physicochemical properties. These methods were then applied to analyze the ITC contents in plants produced in Alsace. Our results highlighted a qualitative and quantitative diversity of the ITC contents, depending on the species and on the variety of Brassicaceae. Indeed; antibacterial and anticancer activity tests were carried out in order to select the most effective molecular species. Antibacterial activity test showed that the effectiveness of ITCs on bacterial cells inhibition was related to bacterial species itself and the chemical structure of the side chain of ITCs as well as their concentration. Anti-cancer activity tests showed that ITCs are able to inhibit colon cancer cells.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Interdomain interactions reveal the molecular evolution of the orange carotenoid protein

International audienceThe photoactive orange carotenoid protein (OCP) is a blue-light intensity sensor involved in cyanobacterial photoprotection. Three OCP families co-exist (OCPX, OCP1 and OCP2), having originated from the fusion of ancestral domain genes. Here, we report the characterization of an OCPX and the evolutionary characterization of OCP paralogues focusing on the role of the linker connecting the domains. The addition of the linker with specific amino acids enabled the photocycle of the OCP ancestor. OCPX is the paralogue closest to this ancestor. A second diversification gave rise to OCP1 and OCP2. OCPX and OCP2 present fast deactivation and weak antenna interaction. In OCP1, OCP deactivation became slower and interaction with the antenna became stronger, requiring a further protein to detach OCP from the antenna and accelerate its deactivation. OCP2 lost the tendency to dimerize, unlike OCPX and OCP1, and the role of its linker is slightly different, giving less controlled photoactivation

In Vitro Reconstitution of the Cyanobacterial Photoprotective Mechanism Mediated by the Orange Carotenoid Protein in Synechocystis PCC 6803[C][W]

In the cyanobacterial photoprotective mechanism, one red-activated Orange Carotenoid Protein binds to the core of the phycobilisome and quenches all its fluorescence. This binding stabilizes the red form. Addition of the Fluorescence Recovery Protein accelerates fluorescence recovery in darkness by interacting with the red protein and destabilizing its binding to the phycobilisome