Uptake of phosphate by two cyanophytes: cation effects and energetics

1987 ◽  
Vol 65 (9) ◽  
pp. 1901-1907 ◽  
Author(s):  
K. Budd ◽  
G. W. Kerson
Keyword(s):  
Membrane Potential ◽  
Phosphate Uptake ◽  
Maximum Velocity ◽  
Proton Motive Force ◽  
Phosphate Transporter ◽  
Saturation Concentration ◽  
Cation Effects ◽  
Synechococcus Leopoliensis ◽  
Metallic Cations ◽  
Significant Uptake

Phosphate uptake in the cyanophytes Synechococcus leopoliensis and Oscillatoria limnetica did not require exogenous metallic cations. In O. limnetica phosphate uptake was described by a single Michaelis–Menten relationship between 0.2 and 10.0 μM phosphate. Calcium increased the maximum velocity and decreased the half-saturation concentration for this system; phosphate uptake was also enhanced by Sr2+ and by Mg2+ but not by Na+, K+, or Zn2+ at up to 1 mM. Calcium appeared to act upon the phosphate transporter and its action is suggested to be ecologically significant. Uptake of phosphate in the light by both cyanophytes was unaffected by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) but was abolished by carbonylcyanide m-chlorophenylhydrazone (CCCP) or dicyclohexylcarbodiimide (DCCD) at concentrations that abolished apparent photosynthesis; however, phosphate uptake was not inhibited by concentrations of CCCP or DCCD that were only slightly inhibitory to apparent photosynthesis. At 5 μM, CCCP abolished light hyperpolarization of the membrane potential but was noninhibitory to phosphate uptake. Phosphate uptake in O. limnetica was accompanied by hyperpolarization of the membrane potential. Gramicidin hyperpolarized the membrane but did not influence phosphate uptake. It is suggested that phosphate uptake in both cyanophytes is independent of the proton motive force.

scholarly journals Evidence of an intestinal phosphate transporter alternative to type IIb sodium-dependent phosphate transporter in rats with chronic kidney disease

2020 ◽  
Vol 36 (1) ◽  
pp. 68-75
Author(s):  
Yasuhiro Ichida ◽  
Shuichi Ohtomo ◽  
Tessai Yamamoto ◽  
Naoaki Murao ◽  
Yoshinori Tsuboi ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Chronic Kidney Disease ◽  
Kidney Disease ◽  
Mrna Expression ◽  
Messenger Rna ◽  
Phosphate Uptake ◽  
Maximum Velocity ◽  
Phosphate Transport ◽  
Phosphate Transporter ◽  
Sodium Dependent

Abstract Background Phosphate is absorbed in the small intestine via passive flow and active transport.NaPi-IIb, a type II sodium-dependent phosphate transporter, is considered to mediate active phosphate transport in rodents. To study the regulation of intestinal phosphate transport in chronic kidney disease (CKD), we analyzed the expression levels of NaPi-IIb, pituitary-specific transcription factor 1 (PiT-1) and PiT-2 and the kinetics of intestinal phosphate transport using two CKD models. Methods CKD was induced in rats via adenine orThy1 antibody injection. Phosphate uptake by intestinal brush border membrane vesicles (BBMV) and the messenger RNA (mRNA) expression of NaPi-IIb, PiT-1 and PiT-2 were analyzed. The protein expression level of NaPi-IIb was measured by mass spectrometry (e.g. liquid chromatography tandem mass spectrometry). Results In normal rats, phosphate uptake into BBMV consisted of a single saturable component and its Michaelis constant (Km) was comparable to that of NaPi-IIb. The maximum velocity (Vmax) correlated with mRNA and protein levels of NaPi-IIb. In the CKD models, intestinal phosphate uptake consisted of two saturable components. The Vmax of the higher-affinity transport, which is thought to be responsible for NaPi-IIb, significantly decreased and the decrease correlated with reduced NaPi-IIb expression. The Km of the lower-affinity transport was comparable to that of PiT-1 and -2. PiT-1 mRNA expression was much higher than that of PiT-2, suggesting that PiT-1 was mostly responsible for phosphate transport. Conclusions This study suggests that the contribution of NaPi-IIb to intestinal phosphate absorption dramatically decreases in rats with CKD and that a low-affinity alternative to NaPi-IIb, in particular PiT-1, is upregulated in a compensatory manner in CKD.

Type 1 Sodium-Dependent Phosphate Transporter acts as a Membrane Potential-Driven Urate Exporter

2013 ◽  
Vol 6 (2) ◽  
pp. 88-94 ◽  
Author(s):  
Takaaki Miyaji ◽  
Tatsuya Kawasaki ◽  
Natsuko Togawa ◽  
Hiroshi Omote ◽  
Yoshinori Moriyama
Keyword(s):  
Membrane Potential ◽  
Phosphate Transporter ◽  
Sodium Dependent

scholarly journals A Constitutive Expressed Phosphate Transporter, OsPht1;1, Modulates Phosphate Uptake and Translocation in Phosphate-Replete Rice

2012 ◽  
Vol 159 (4) ◽  
pp. 1571-1581 ◽  
Author(s):  
Shubin Sun ◽  
Mian Gu ◽  
Yue Cao ◽  
Xinpeng Huang ◽  
Xiao Zhang ◽  
...  
Keyword(s):  
Phosphate Uptake ◽  
Phosphate Transporter

Proton motive force as a function of the pH at which Methanobacterium bryantii is grown

1985 ◽  
Vol 31 (11) ◽  
pp. 1031-1034 ◽  
Author(s):  
G. Dennis Sprott ◽  
Sharon E. Bird ◽  
Ian J. McDonald
Keyword(s):  
Membrane Potential ◽  
Proton Motive Force ◽  
Motive Force ◽  
Ph Gradient ◽  
Alkaline Media ◽  
Cytoplasmic Ph ◽  
Acidic Media ◽  
Generation Times ◽  
Optimum Ph ◽  
Ph Range

Methanobacterium bryantii was grown on CO2 and H2 over a pH range between the extremes of 5.0 and 8.1. Generation times were shortest between pH 6.6 and 7.1. Cells grown at optimum pH had a proton motive force consisting predominantly of the membrane potential but those grown at nonoptimal pH generated a transmembrane pH gradient as well. This pH gradient was, however, insufficient to maintain a constant cytoplasmic pH during growth in very acidic or basic media. The results suggest that in acidic media growth may be limited by the cytoplasmic pH and that in alkaline media it may be limited by the cytoplasmic pH and (or) by the magnitude of the proton motive force.

scholarly journals Is Myelin a Mitochondrion?

2012 ◽  
Vol 33 (1) ◽  
pp. 33-36 ◽  
Author(s):  
Julia J Harris ◽  
David Attwell
Keyword(s):  
Membrane Potential ◽  
Respiratory Chain ◽  
Atp Synthase ◽  
Proton Motive Force ◽  
Motive Force ◽  
Myelin Membrane ◽  
Considerable Doubt

It has been hypothesized that myelin acts like a mitochondrion, generating ATP across the membranes of its sheath. By calculating the proton motive force across the myelin membrane based on known values for the pH and membrane potential of the oligodendrocyte, we find that insufficient energy could be harvested from proton flow across the myelin membrane to synthesize ATP. In fact, if the respiratory chain were present in the myelin membrane, then the ATP synthase would function in reverse, hydrolyzing rather than synthesizing ATP. This calculation places the hypothesis of an energy-producing role for myelin in considerable doubt.

L-Malate transport and proton symport in vesicles prepared from Pseudomonas putida

1986 ◽  
Vol 64 (11) ◽  
pp. 1190-1194 ◽  
Author(s):  
F. R. Agbanyo ◽  
G. Moses ◽  
N. F. Taylor
Keyword(s):  
Membrane Potential ◽  
Pseudomonas Putida ◽  
Kinetic Analysis ◽  
Transport System ◽  
Electron Donor ◽  
Proton Transport ◽  
Proton Motive Force ◽  
Alkaline Ph ◽  
Proton Symport ◽  
Malate Transport

In vesicles from glucose-grown Pseudomonas putida, L-malate is transported by nonspecific physical diffusion. L-Malate also acts as an electron donor and generates a proton motive force (Δp) of 129 mV which is composed of a membrane potential (Δψ) of 60 mV and a ΔpH of 69 mV. In contrast, vesicles from succinate-grown cells (a) transport L-malate by a carrier-mediated system with a Km value of 14.3 mM and a Vmax of 313 nmol∙mg protein−1∙min−1, (b) generate no Δψ, ΔpH, or Δp when L-malate is the electron donor, and (c) produce an extravesicular alkaline pH during the transport of L-malate. A kinetic analysis of this L-malate-induced proton transport gives a Km value of 16 mM and a Vmax of 667 nmol H+∙mg protein−1∙min−1. This corresponds to a H+/L-malate ratio of 2.1. The failure to generate a Δp in these vesicles is considered, therefore, to be consistent with the induction in succinate-grown cells of an electrogenic proton symport L-malate transport system.

scholarly journals The effects of partial and selective reduction in the components of the proton-motive force on lactose uptake in Escherichia coli

1981 ◽  
Vol 200 (3) ◽  
pp. 583-589 ◽  
Author(s):  
S Ahmed ◽  
I R Booth
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Membrane Potential ◽  
Selective Reduction ◽  
Proton Motive Force ◽  
Motive Force ◽  
Ph Gradient ◽  
A Value ◽  
The Relationship ◽  
Lactose Transport

The relationship between the steady state lactose accumulation (delta plac) and the magnitude of the membrane potential (delta psi) and pH gradient (delta pH) has been studied at pHo5.5 and pHo7.5. An attempt has been made to differentiate between two possible means by which lactose accumulation may be reduced below the proton-motive force (delta p). Firstly, that delta psi and delta pH are not equivalent in driving lactose transport and secondly, that ‘slip’ reactions (beta-galactoside exit via the carrier without a proton) may reduce accumulation. The data support the latter; however, our conclusions are tempered by the observation that the apparent stoichiometry (delta plac/delta p) increases to a value of at least 2 at values of delta p below 130 mV.

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