ATP-dependent transport systems in the canalicular membrane of the hepatocyte.

1995 ◽  
Vol 75 (2) ◽  
pp. 261-275 ◽  
Author(s):  
Z C Gatmaitan ◽  
I M Arias
Keyword(s):  
Transport Systems ◽  
Canalicular Membrane ◽  
Dependent Transport

Adaptation of phosphate transport in phosphate-deprived LLC-PK1 cells

1985 ◽  
Vol 248 (1) ◽  
pp. F122-F127 ◽  
Author(s):  
J. Caverzasio ◽  
C. D. Brown ◽  
J. Biber ◽  
J. P. Bonjour ◽  
H. Murer
Keyword(s):  
Adaptive Response ◽  
Apical Membrane ◽  
Specific Activity ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Linear Process ◽  
Transport Systems ◽  
Experimental Systems ◽  
Cotransport System ◽  
Dependent Transport

Sodium-dependent transport of phosphate was studied in LLC-PK1 cells that had been deprived of phosphate (Pi). Compared with control cells (fed with 2 mM Pi) a twofold increase in the rate of Na-Pi cotransport was observed in cells incubated for 15 h in a phosphate-free medium, whereas transport of L-alanine and the specific activity of alkaline phosphatase were not changed. The same adaptive response was observed with apical membrane vesicles isolated from Pi-deprived cells. In both experimental systems Pi deprivation caused a change in the Vmax but not in the apparent Km (for Pi) of the cotransport system. Adaptation of the Na-Pi cotransport was triggered by free phosphate concentrations between 0 and 100 microM. Over the first 20 h the adaptive response was found to be a linear process that could be prevented by 70 microM cycloheximide. Adapted cells that were re-treated with phosphate showed a rapid (less than 3 h) decrease in the Na-Pi transport. The data suggest that LLC-PK1 cells adapt to low Pi conditions by increasing the rate of the Na-Pi cotransport, which is located in the apical membrane. Two mechanisms may be involved in the adaptive response: a long-term process involving new protein synthesis, and a short-term response involving activation-inactivation of transport systems already existing.

scholarly journals Redundancy in Periplasmic Binding Protein-Dependent Transport Systems for Trehalose, Sucrose, and Maltose in Sinorhizobium meliloti

2002 ◽  
Vol 184 (11) ◽  
pp. 2978-2986 ◽  
Author(s):  
John Beck Jensen ◽  
N. Kent Peters ◽  
T. V. Bhuvaneswari
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Binding Protein ◽  
Regulatory Protein ◽  
Gene Replacement ◽  
Transport Systems ◽  
Atp Binding ◽  
Dependent Transport ◽  
Atp Binding Protein ◽  
Growth Experiments

ABSTRACT We have identified a cluster of six genes involved in trehalose transport and utilization (thu) in Sinorhizobium meliloti. Four of these genes, thuE, -F, -G, and -K, were found to encode components of a binding protein-dependent trehalose/maltose/sucrose ABC transporter. Their deduced gene products comprise a trehalose/maltose-binding protein (ThuE), two integral membrane proteins (ThuF and ThuG), and an ATP-binding protein (ThuK). In addition, a putative regulatory protein (ThuR) was found divergently transcribed from the thuEFGK operon. When the thuE locus was inactivated by gene replacement, the resulting S. meliloti strain was impaired in its ability to grow on trehalose, and a significant retardation in growth was seen on maltose as well. The wild type and the thuE mutant were indistinguishable for growth on glucose and sucrose. This suggested a possible overlap in function of the thuEFGK operon with the aglEFGAK operon, which was identified as a binding protein-dependent ATP-binding transport system for sucrose, maltose, and trehalose. The Km s for trehalose transport were 8 ± 1 nM and 55 ± 5 nM in the uninduced and induced cultures, respectively. Transport and growth experiments using mutants impaired in either or both of these transport systems show that these systems form the major transport systems for trehalose, maltose, and sucrose. By using a thuE′-lacZ fusion, we show that thuE is induced only by trehalose and not by cellobiose, glucose, maltopentaose, maltose, mannitol, or sucrose, suggesting that the thuEFGK system is primarily targeted toward trehalose. The aglEFGAK operon, on the other hand, is induced primarily by sucrose and to a lesser extent by trehalose. Tests for root colonization, nodulation, and nitrogen fixation suggest that uptake of disaccharides can be critical for colonization of alfalfa roots but is not important for nodulation and nitrogen fixation per se.

Periplasmic binding protein-dependent transport systems: the membrane-associated components

1990 ◽  
Vol 326 (1236) ◽  
pp. 353-365 ◽  
Keyword(s):  
Transport System ◽  
Atp Hydrolysis ◽  
Binding Protein ◽  
Primary Source ◽  
Energy Coupling ◽  
Transport Systems ◽  
Common Mechanism ◽  
Atp Binding ◽  
Periplasmic Binding Protein ◽  
Dependent Transport

Periplasmic binding protein-dependent transport systems are multicomponent, consisting of several inner membrane-associated proteins and a periplasmic component. The membrane-associated components of different systems are related in organization and function suggesting that, despite different substrate specificities, each transport system functions by a common mechanism. Current understanding of these components is reviewed. The nature of energy coupling to periplasmic transport systems has long been debated. Recent data now demonstrate that ATP hydrolysis is the primary source of energy for transport. The ATP-binding transport components are the best characterized of a family of closely related ATP-binding proteins believed to couple ATP hydrolysis to a variety of different biological processes. Intriguingly, systems closely related to periplasmic binding protein-dependent transport systems have recently been identified in several Gram-positive organisms (which lack a periplasm) and in eukaryotic cells. This class of transport system appears to be widespread in nature, serving a variety of important and diverse functions.

ATP-dependent transport of beta-estradiol 17-(beta-D-glucuronide) in rat canalicular membrane vesicles

1996 ◽  
Vol 271 (5) ◽  
pp. G791-G798
Author(s):  
M. Vore ◽  
T. Hoffman ◽  
M. Gosland
Keyword(s):  
Bile Acid ◽  
Transport System ◽  
Organic Anion ◽  
Membrane Vesicles ◽  
Anion Transport ◽  
Organic Anion Transport ◽  
Canalicular Membrane ◽  
P Glycoprotein ◽  
Anion Transport System ◽  
Dependent Transport

The ATP-dependent transport of beta-estradiol 17-(beta-D-glucuronide) (E217G), a cholestatic metabolite of estradiol, was investigated in rat liver canalicular membrane vesicles. ATP-dependent transport was dependent on time and temperature and occurred into an osmotically sensitive space; kinetic analysis indicated a saturable transport system (Michaelis-Menten constant value, 75 microM; maximum transport rate, 598 pmol.min-1.mg protein-1). The steroid conjugates estradiol glucuronide, estriol 3-glucuronide, estriol 16 alpha-glucuronide, testosterone glucuronide, and the three-sulfate conjugate of 17G were effective inhibitors of transport. Bromosulfophthalein, S-(2,4-dinitrophenyl)glutathione, and glutathione disulfide, all substrates of the canalicular ATP-dependent non-bile acid organic anion transport system, were also effective inhibitors, whereas taurocholate had no effect on transport. Conversely, E217G inhibited the ATP-dependent transport of S-(2,4-dinitrophenyl)glutathione. Daunorubicin, vinblastine, etoposide, cyclosporin, and PSC-833, substrates/modulators of P-glycoprotein, were also potent inhibitors of E217G transport, and E217G competitively inhibited the ATP-dependent transport of daunorubicin. C219, a monoclonal antibody against P-glycoprotein, inhibited ATP-dependent transport of E217G and daunorubicin but not of taurocholate or S-(2,4-dinitrophenyl)glutathione. These data indicate that E217G is substrate of both the non-bile acid organic anion transport system and P-glycoprotein but not of the ATP-dependent bile acid transport system in canalicular membranes.

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