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Cyanide M (cyanide + m)
Kinds of Cyanide M Selected AbstractsIntracellular pH homeostasis in the filamentous fungus Aspergillus nigerFEBS JOURNAL, Issue 14 2002Stephan J. A. Hesse Intracellular pH homeostasis in the filamentous fungus Aspergillus niger was measured in real time by 31P NMR during perfusion in the NMR tube of fungal biomass immobilized in Ca2+ -alginate beads. The fungus maintained constant cytoplasmic pH (pHcyt) and vacuolar pH (pHvac) values of 7.6 and 6.2, respectively, when the extracellular pH (pHex) was varied between 1.5 and 7.0 in the presence of citrate. Intracellular metabolism did not collapse until a ,pH over the cytoplasmic membrane of 6.6,6.7 was reached (pHex 0.7,0.8). Maintenance of these large pH differences was possible without increased respiration compared to pHex 5.8. Perfusion in the presence of various hexoses and pentoses (pHex 5.8) revealed that the magnitude of ,pH values over the cytoplasmic and vacuolar membrane could be linked to the carbon catabolite repressing properties of the carbon source. Also, larger ,pH values coincided with a higher degree of respiration and increased accumulation of polyphosphate. Addition of protonophore (carbonyl cyanide m -chlorophenylhydrazone, CCCP) to the perfusion buffer led to decreased ATP levels, increased respiration and a partial (1 µm CCCP), transient (2 µm CCCP) or permanent (10 µm CCCP) collapse of the vacuolar membrane ,pH. Nonlethal levels of the metabolic inhibitor azide (N3,, 0.1 mm) caused a transient decrease in pHcyt that was closely paralleled by a transient vacuolar acidification. Vacuolar H+ influx in response to cytoplasmic acidification, also observed during extreme medium acidification, indicates a role in pH homeostasis for this organelle. Finally, 31P NMR spectra of citric acid producing A. niger mycelium showed that despite a combination of low pHex (1.8) and a high acid-secreting capacity, pHcyt and pHvac values were still well maintained (pH 7.5 and 6.4, respectively). [source] On the kinetics of voltage formation in purple membranes of Halobacterium salinariumFEBS JOURNAL, Issue 19 2000Richard W. Hendler The kinetics of the bacteriorhodopsin photocycle, measured by voltage changes in a closed membrane system using the direct electrometrical method (DEM) of Drachev, L.A., Jasaitus, A.A., Kaulen, A.D., Kondrashin, A.A., Liberman, E.A., Nemecek, I.B., Ostroumov, S.A., Semenov, Yu, A. & Skulachev, V.P. (1974) Nature249, 321,324 are sixfold slower than the kinetics obtained in optical studies with suspensions of purple membrane patches. In this study, we have investigated the reasons for this discrepancy. In the presence of the uncouplers carbonyl cyanide m -chlorophenylhydrazone or valinomycin, the rates in the DEM system are similar to the rates in suspensions of purple membrane. Two alternative explanations for the effects of uncouplers were evaluated: (a) the ,back-pressure' of the ,µ,H+ slows the kinetic steps leading to its formation, and (b) the apparent difference between the two systems is due to slow major electrogenic events that produce little or no change in optical absorbance. In the latter case, the uncouplers would decrease the RC time constant for membrane capacitance leading to a quicker discharge of voltage and concomitant decrease in photocycle turnover time. The experimental results show that the primary cause for the slower kinetics of voltage changes in the DEM system is thermodynamic back-pressure as described by Westerhoff, H.V. & Dancshazy, Z. (1984) Trends Biochem. Sci.9, 112,117. [source] Presence of a Na+ -stimulated P-type ATPase in the plasma membrane of the alkaliphilic halotolerant cyanobacterium Aphanothece halophyticaFEMS MICROBIOLOGY LETTERS, Issue 1 2007Kanjana Wiangnon Abstract Aphanothece cells could take up Na+ and this uptake was strongly inhibited by the protonophore, carbonyl cyanide m -chlorophenylhydrazone (CCCP). Cells preloaded with Na+ exhibited Na+ extrusion ability upon energizing with glucose. Na+ was also taken up by the plasma membranes supplied with ATP and the uptake was abolished by gramicidin D, monensin or Na+ -ionophore. Orthovanadate and CCCP strongly inhibited Na+ uptake, whereas N, N, -dicyclohexylcarbodiimide (DCCD) slightly inhibited the uptake. Plasma membranes could hydrolyse ATP in the presence of Na+ but not with K+, Ca2+ and Li+. The Km values for ATP and Na+ were 1.66±0.12 and 25.0±1.8 mM, respectively, whereas the Vmax value was 0.66±0.05 ,mol min,1 mg,1. Mg2+ was required for ATPase activity whose optimal pH was 7.5. The ATPase was insensitive to N -ethylmaleimide, nitrate, thiocyanate, azide and ouabain, but was substantially inhibited by orthovanadate and DCCD. Amiloride, a Na+/H+ antiporter inhibitor, and CCCP showed little or no effect. Gramicidin D and monensin stimulated ATPase activity. All these results suggest the existence of a P-type Na+ -stimulated ATPase in Aphanothece halophytica. Plasma membranes from cells grown under salt stress condition showed higher ATPase activity than those from cells grown under nonstress condition. [source] Carbonyl cyanide m -chlorophenylhydrazone induced calcium signaling and activation of plasma membrane H+ -ATPase in the yeast Saccharomyces cerevisiaeFEMS YEAST RESEARCH, Issue 4 2008Michele B.P. Pereira Abstract The plasma membrane H+ -ATPase from Saccharomyces cerevisiae is an enzyme that plays a very important role in the yeast physiology. The addition of protonophores, such as 2,4-dinitrophenol (DNP) and carbonyl cyanide m -chlorophenylhydrazone (CCCP), also triggers a clear in vivo activation of this enzyme. Here, we demonstrate that CCCP-induced activation of the plasma membrane H+ -ATPase shares some similarities with the sugar-induced activation of the enzyme. Phospholipase C and protein kinase C activities are essential for this activation process while Gpa2p, a G protein involved in the glucose-induced activation of the ATPase, is not required. CCCP also induces a phospholipase C-dependent increase in intracellular calcium. Moreover, we show that the availability of extracellular calcium is required for CCCP stimulation of H+ -ATPase, suggesting a possible connection between calcium signaling and activation of ATPase. [source] Chemical induction of rapid and reversible plastid filamentation in Arabidopsis thaliana rootsPHYSIOLOGIA PLANTARUM, Issue 2 2010Ryuuichi D. Itoh Plastids assume various morphologies depending on their developmental status, but the basis for developmentally regulated plastid morphogenesis is poorly understood. Chemical induction of alterations in plastid morphology would be a useful tool for studying this; however, no such chemicals have been identified. Here, we show that antimycin A, an effective respiratory inhibitor, can change plastid morphology rapidly and reversibly in Arabidopsis thaliana. In the root cortex, hypocotyls, cotyledon epidermis and true leaf epidermis, significant differences in mitochondrial morphology were not observed between antimycin-treated and untreated tissues. In contrast, antimycin caused extreme filamentation of plastids in the mature cortices of main roots. This phenomenon was specifically observed in the mature root cortex. Other mitochondrial respiratory inhibitors (rotenone and carbonyl cyanide m -chlorophenylhydrazone), hydrogen peroxide, S -nitroso- N -acetylpenicillamine [a nitric oxide (NO) donor] and 3-(3,4-dichlorophenyl)-1,1-dimethylurea did not mimic the phenomenon under the present study conditions. Antimycin-induced plastid filamentation was initiated within 5 min after the onset of chemical treatment and appeared to complete within 1 h. Plastid morphology was restored within 7 h after the washout of antimycin, suggesting that the filamentation was reversible. Co-applications of antimycin and cytoskeletal inhibitors (demecolcine or latrunculin B) or protein synthesis inhibitors (cycloheximide or chloramphenicol) still caused plastid filamentation. Antimycin A was also effective for plastid filamentation in the chloroplast division mutants atftsZ1-1 and atminE1. Salicylhydroxamic acid, an alternative oxidase inhibitor, was solely found to suppress the filamentation, implying the possibility that this phenomenon was partly mediated by an antimycin-activated alternative oxidase in the mitochondria. [source] | ||||||||||