Active CO2 transport in cyanobacteria

1991 ◽  
Vol 69 (5) ◽  
pp. 925-935 ◽  
Author(s):  
Anthony G. Miller ◽  
George S. Espie ◽  
David T. Canvin
Keyword(s):  
Transport System ◽  
Ph Regulation ◽  
Metabolic Energy ◽  
Metabolic Inhibitors ◽  
Active Process ◽  
Transport Models ◽  
Key Words Cyanobacteria ◽  
Present Evidence ◽  
Dense Cell ◽  
Active Transport System

Cyanobacteria appear to possess an active transport system for molecular CO2. This system, first discovered by Badger and Andrews in 1982 (1982. Plant Physiol. 70: 517–523), is without reported precedence in the bacterial, animal, or plant literature. The transport system operates so efficiently that in dense cell suspensions the extracellular CO2 concentration is pulled far below the equilibrium value. This CO2 drawdown is not due to CO2 fixation but can be accounted for by a transport system that recognizes molecular CO2 and causes it to be transported into the cell. The fact that operation of the system causes a massive disequilibration of the extracellular CO2–HCO3− system means that there must be an expenditure of metabolic energy. The CO2 is actually moved against a considerable CO2 concentration gradient. In this review we discuss methods that can be used to monitor CO2 transport in cyanobacteria. We present evidence that CO2 transport is an active process. It is emphasized that little is known about the concomitant ion fluxes that must occur to ensure charge and pH regulation during CO2 transport. Key words: cyanobacteria, active CO2 transport, metabolic inhibitors, transport models.

scholarly journals Coregulation of beta-galactoside uptake and hydrolysis by the hyperthermophilic bacterium Thermotoga neapolitana

1997 ◽  
Vol 63 (3) ◽  
pp. 969-972
Author(s):  
MY Galperin ◽  
KM Noll ◽  
AH Romano
Keyword(s):  
Active Transport ◽  
Transport System ◽  
Metabolic Energy ◽  
Free Sugar ◽  
Thermotoga Neapolitana ◽  
Inducer Exclusion ◽  
Hyperthermophilic Bacterium ◽  
Active Transport System ◽  
Hydrolysis Of ◽  
Beta Galactosidase

Regulation of the beta-galactoside transport system in response to growth substrates in the extremely thermophilic anaerobic bacterium Thermotoga neapolitana was studied with the nonmetabolizable analog methyl-beta-D-thiogalactopyranoside (TMG) as the transport substrate. T. neapolitana cells grown on galactose or lactose accumulated TMG against a concentration gradient in an intracellular free sugar pool that was exchangeable with external galactose or lactose and showed induced levels of beta-galactosidase. Cells grown on glucose, maltose, or galactose plus glucose showed no capacity to accumulate TMG, though these cells carried out active transport of the nonmetabolizable glucose analog 2-deoxy-D-glucose. Glucose neither inhibited TMG uptake nor caused efflux of preaccumulated TMG; rather, glucose promoted TMG uptake by supplying metabolic energy. These data show that beta-D-galactosides are taken up by T. neapolitana via an active transport system that can be induced by galactose or lactose and repressed by glucose but which is not inhibited by glucose. Thus, the phenomenon of catabolite repression is present in T. neapolitana with respect to systems catalyzing both the transport and hydrolysis of beta-D-galactosides, but inducer exclusion and inducer expulsion, mechanisms that regulate permease activity, are not present. Regulation is manifest at the level of synthesis of the beta-galactoside transport system but not in the activity of the system.

Defective Active Glucose Transport in Platelets of Atherosclerotic Patients

1979 ◽  
Author(s):  
T.U. Yardimci
Keyword(s):  
Glucose Transport ◽  
Active Transport ◽  
Transport System ◽  
Human Platelets ◽  
Metabolic Energy ◽  
Metabolic Inhibitors ◽  
Temperature Dependent ◽  
Glucose Transport System ◽  
Normal Human

The glucose transport system in normal human platelets is temperature dependent and is a saturable process obeying Michaelis Menten Kinetics. It is inhibited by DNP, KCN, NaN3 and by Oubain. Therefore this system uses cells’ metabolic energy and/or is coupled to Na+ gradient. The Km of this system is 3.44±0.91x10-5 M and V max is 2.03±0.13 nmole/109 pietelets/30". 3-0-methylglucose does not use the same transport system whereas 2-deoxyglucose inhibits the glucose transport in platelets. In the platelets of nondiabetic atherosclerotic patients showing hypercoagulability, the active transport of glucose is decreased. In most of the tases this system is temperature insensitive, and is insensitive to metabolic inhibitors. The importance ot this alteration in the pathogenesis of atherosclerosis is discussed.

On the structural organization of biological pumps and channels

1984 ◽  
Vol 42 ◽  
pp. 138-141
Author(s):  
G. Zampighi ◽  
M. Kreman
Keyword(s):  
Active Transport ◽  
Transport System ◽  
Plasma Membranes ◽  
Transport Proteins ◽  
Molecular Organization ◽  
Passive Transport ◽  
Concentration Gradients ◽  
Cell Functions ◽  
Natural Concentration ◽  
Active Transport System

The plasma membranes of most animal cells contain transport proteins which function to provide passageways for the transported species across essentially impermeable lipid bilayers. The channel is a passive transport system which allows the movement of ions and low molecular weight molecules along their concentration gradients. The pump is an active transport system and can translocate cations against their natural concentration gradients. The actions and interplay of these two kinds of transport proteins control crucial cell functions such as active transport, excitability and cell communication. In this paper, we will describe and compare several features of the molecular organization of pumps and channels. As an example of an active transport system, we will discuss the structure of the sodium and potassium ion-activated triphosphatase [(Na+ +K+)-ATPase] and as an example of a passive transport system, the communicating channel of gap junctions and lens junctions.

scholarly journals Actions of external hypertonic urea, ADH, and theophylline on transcellular and extracellular solute permeabilities in frog skin.

1975 ◽  
Vol 65 (5) ◽  
pp. 599-615 ◽  
Author(s):  
L J Mandel
Keyword(s):  
Linear Relationship ◽  
Active Transport ◽  
Transport System ◽  
Frog Skin ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Solute Permeability ◽  
Parallel Lines ◽  
Paracellular Pathways ◽  
Active Transport System

Increases in transepithelial solute permeability were elicited in the frog skin with external hypertonic urea, theophylline, and vasopressin (ADH). In external hypertonic urea, which is known to increase the permeability of the extracellular (paracellular) pathway, the unidirectional transepithelial fluxes of Na (passive), K, Cl, and urea increased substantially while preserving a linear relationship to each other. The same linear relationship was also observed for the passive Na and urea fluxes in regular Ringer and under stimulation with ADH or 10 mM theophylline, indicating that their permeation pathway was extracellular. A linear relationship between Cl and urea fluxes could be demonstrated if the skins were separated according to their open circuit potentials; parallel lines were obtained with increasing intercepts on the Cl axis as the open circuit potential decreased. The slopes of the Cl vs. urea lines were not different from that obtained in external hypertonic urea, indicating that this relationship described the extracellular movement of Cl. The intercept on the ordinate was interpreted as the contribution from the transcellular Cl movement. In the presence of 0.5 mM theophylline or 10 mU/ml of ADH, mainly the transcellular movement of Cl increased, whereas 10 mM theophylline caused increases in both transcellular and extracellular Cl fluxes. These and other data were interpreted in terms of a possible intracellular control of the theophylline-induced increase in extracellular fluxes. The changes in passive solute permeability were shown to be independent of active transport. The responses of the active transport system, the transcellular and paracellular pathways to theophylline and ADH could be explained in terms of the different resulting concentrations of cyclic 3'-5'-AMP produced by each of these substances in the tissue.

Influence of Irradiance on H+ Efflux and Cl- Influx in Chara corallina: An Investigation Aimed at Testing Two Cl- Transport Models

1976 ◽  
Vol 3 (4) ◽  
pp. 443
Author(s):  
W.J Lucas ◽  
F.A Smith
Keyword(s):  
Transport System ◽  
Energy Supply ◽  
Chara Corallina ◽  
Maximum Activity ◽  
Present Form ◽  
Significant Modification ◽  
Transport Models ◽  
Experimental Conditions ◽  
Cl Transport ◽  
Lag Period

Parallel studies on the influence of irradiance on net H+ efflux and *36Cl- uptake were conducted on C. corallina. Following the dark-to-light transition, a lag period of 8-15 min was observed before net H+ efflux activity could be discerned experimentally. Decreasing the irradiance did not significantly lengthen this lag period. Studies on *36Cl- uptake revealed that a lag period of 40-60 min was required before the Cl- transport system attained maximum activity, governed by the prevailing experimental conditions. These results are discussed in relation to the Cl- transport hypotheses proposed by Spear et al. and by Smith. It would seem that the hypothesis of Spear et al., in its present form, is invalid for Chara corallina. The results were inconclusive in terms of support (or otherwise) for a Cl-/OH- antiporter. However, the Cl-/OH- antiporter hypothesis originally proposed by Smith will require significant modification, especially in terms of the energy supply.

A linked active transport system for Na+ and K+ in a glial cell line

1976 ◽  
Vol 104 (1) ◽  
pp. 93-105 ◽  
Author(s):  
Gary Kukes ◽  
Jean De Vellis ◽  
Rafael Elul
Keyword(s):  
Cell Line ◽  
Glial Cell ◽  
Active Transport ◽  
Transport System ◽  
Active Transport System

The pH-dependent uptake of putrescine by Pseudomonas acidovorans and its incorporation into bacteriophage DNA

1983 ◽  
Vol 29 (7) ◽  
pp. 827-829 ◽  
Author(s):  
D. L. Bruce ◽  
R. A. J. Warren
Keyword(s):  
Active Transport ◽  
Transport System ◽  
Normal Condition ◽  
Intracellular Pool ◽  
Pseudomonas Acidovorans ◽  
Ph Dependent ◽  
Active Transport System

Lack of an active transport system prevents Pseudomonas acidovorans taking up putrescine under normal condition of growth. At pH 9.5, however, putrescine does enter the cell. That putrescine enters the intracellular pool is shown by its conversion to 2-hydroxyputrescine and spermidine after the cells are returned to pH 7.0. The accumulated putrescine can be used to label specifically the α-putrescinylthymine residues of bacteriophage [Formula: see text] DNA.

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