Proton‐coupled hexose transport in <i>Chlorella vulgaris</i>

Komor, Ewald

doi:10.1016/0014-5793(73)80501-0

Cited by 132 publications

(49 citation statements)

References 10 publications

(9 reference statements)

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“…It is capable of accumulative transport of hexose analogues using HI gradients for electrogenic secondary active transport (4)(5)(6)(7). The cDNA of this transporter has been cloned (HUP); hexose uptake protein 1) and its identity has been proven by heterologous expression in Schizosaccharomyces pombe (8,9).…”

mentioning

confidence: 99%

Km mutants of the Chlorella monosaccharide/H+ cotransporter randomly generated by PCR.

Will

Caspari²,

Tanner³

1994

Proc. Natl. Acad. Sci. U.S.A.

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The HUPI gene codes for the monosacharide/H+ cotransr protein of Chiorella kesslni. The gene is functionally expressed in Schizosaccharomyces pombe. This heterologous system has been used to screen for K. mutants of the Chorela symporter. Since S. pombe transformed with HUPI cDNA showed a 1000-fold increase in sensitivity toward the toxic sugar analogue 2-deoxyglucose, we screened for transformants with a decreased 2-deoxyglucose sensitivity.

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mentioning

confidence: 99%

Km mutants of the Chlorella monosaccharide/H+ cotransporter randomly generated by PCR.

Will

Caspari²,

Tanner³

1994

Proc. Natl. Acad. Sci. U.S.A.

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“…The recent demonstration in fungi [9,11], plants [12,13] and algae [14] of active transport of nutrients occurring by cotransport with protons suggests a chemiosmotic mechanism where the electrochemical proton gradient generated by the pump is the driving force for nutrient uptake [15]. Therefore, the nature of this proton pump has become one of the most crucial issues in the bioenergetics of lower eukaryotes.…”

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confidence: 99%

Effect of ATPase Inhibitors on the Proton Pump of Respiratory‐Deficient Yeast

Serrano¹

1980

European Journal of Biochemistry

173

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Diethylstilbestrol and dicyclohexylcarbodiimide inhibit the ATPase of the plasma membranes and the proton-pumping activity of the cells in a respiratory-deficient mutant of Succlzaromyces cerevisiue. The effects of the inhibitors in vivo seem to be specific because neither the proton permeability nor the ATP levels of the cells are affected. These results indicate that the yeast plasmamembrane ATPase corresponds to the proton pump of the cells. The fact that both inhibitors of the ATPase delay the fall of ATP levels which follows a block of fermentation indicates that ATPase function is one of the major ATP-consuming pathways in yeast. In addition, diethylstilbestrol prevents the fall of ATP levels produced by dinitrophenol, suggesting that this fall was caused by partial dissipation of the proton gradient and consequent stimulation of the proton-pumping ATPase.The existence of electrogenic proton pumps on the plasma membranes of fungi [1,2], plants [3,4] and algae [5,6] has been postulated on the basis of measurements of membrane potentials with microelectrodes. In yeast cells, probably because the high permeability to potassium and succinate provides electrical balance for proton movements, the activity of the pump is manifested by a massive proton efflux which can reduce the external pH to values as low asThe recent demonstration in fungi [9,11], plants [12,13] and algae [14] of active transport of nutrients occurring by cotransport with protons suggests a chemiosmotic mechanism where the electrochemical proton gradient generated by the pump is the driving force for nutrient uptake [15]. Therefore, the nature of this proton pump has become one of the most crucial issues in the bioenergetics of lower eukaryotes.Conway [16] advanced the hypothesis that the yeast proton pump could be a redox metal catalyst but as the eukaryotic plasma membrane probably lacks respiratory carriers, the function of a proton pump can more plausibly be attributed to an ATPase as has been suggested by Peiia [ 101. Actually, evidence has beenEnzyme. ATPase or adenosine triphosphatase (EC 3.6.1.3).presented in Neurospora crassa which indicates that the membrane potential of both whole cells [l] and isolated plasma membrane vesicles [17] depends on ATP and not on redox processes.Plasma membrane ATPases with similar kinetic properties have been identified in plants [18,19] and fungi [20 -231, including yeast [24]. These enzymes are sensitive to dicyclohexylcarbodiimide and diethylstilbestrol but not to oligomycin. In order to investigate the possibility that theyeast plasma-membrane ATPase corresponds to the proton pump we have studied the effect of ATPase inhibitors on the proton-pumping activity of the cells.For this work we have employed a respiratorydeficient mutant of Saccharomyces cerevisiae. Since these mutants lack functional mitochondria [25], the effects of the inhibitors are not complicated by interference with the oxidative phosphorylation. In addition, as these mutants also lack endogenous metabolism [26] the ATP content o...

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“…It seems to operate in the transport of sugars [1][2][3][4][5] and amino acids [8,9] as well as that of anions like phosphate ( [9,10] and C. I. U. E. et al, unpublished results) and nitrate. This assumption would be in agreement with the hypothesis proposed [6] that the proton extrusion pump is the general driving force for active transport in plant cells.…”

Section: Discussionmentioning

confidence: 90%

“…This was concluded from the transient alkalinization of the external medium [1][2][3] and from the transient depolarization of the membrane [2,4,5] at the onset of sugar transport. The proton-hexose co-transport was supposed to be maintained by an electrochemical proton gradient (A~H ÷) [1--5], in agreement with the co-transport hypothesis proposed [6] for active transport processes through plant membranes in general [6].…”

Section: Introductionmentioning

confidence: 99%