Characterization of aSchizosaccharomyces pombe mutant deficient in UDP-galactose transport activity

Yeast ◽  
2001 ◽  
Vol 18 (10) ◽  
pp. 903-914 ◽  
Author(s):  
Naotaka Tanaka ◽  
Mami Konomi ◽  
Masako Osumi ◽  
Kaoru Takegawa
Keyword(s):  
Transport Activity ◽  
Galactose Transport

Characterization of Na(+)-H+ antiporter activity associated with human cheek epithelial cells

1994 ◽  
Vol 267 (1) ◽  
pp. C84-C93 ◽  
Author(s):  
E. J. McMurchie ◽  
S. L. Burnard ◽  
G. S. Patten ◽  
E. J. Lee ◽  
R. A. King ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Human Subjects ◽  
Maximum Velocity ◽  
Hill Coefficient ◽  
Transport Activity ◽  
Uptake Activity ◽  
Dimethyl Amiloride ◽  
Mouth Wash ◽  
Na Uptake

Na+ transport activity was characterized in human cheek epithelial cells obtained from normotensive adult subjects. The cells were isolated using a mouth-wash procedure and assayed for Na+ uptake using a radioactive (22Na+) rapid filtration assay. Cheek cells displayed proton-dependent Na+ uptake activity that was dependent on the magnitude of the externally directed proton gradient measured using the fluorescent probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein to determine intracellular pH. Amiloride, ethylisopropylamiloride (EIPA), 5-(N,N-dimethyl)-amiloride, 5-(N-methyl-N-isobutyl)-amiloride (MIA), and 5-(N,N-hexamethylene)-amiloride (NNHA) all inhibited proton-dependent Na+ uptake, with MIA, EIPA, and NNHA being the most potent. The Michaelis constant (Km) for extracellular Na+ was 5.7 mM, while the maximum velocity for Na(+)-H+ antiporter activity was 4.3 nmol Na+.mg protein-1.30s-1. The Km for intracellular H+ was 0.17 microM, with a Hill coefficient of 0.7. Stimulation by ouabain and inhibition by bumetanide of cheek cell proton-dependent Na+ uptake indicated only relatively low activities of Na(+)-K(+)-ATPase and Na(+)-K(+)-2Cl- cotransport, respectively. These results are consistent with the presence of Na(+)-H+ antiporter activity in cheek cells. Cheek cells therefore provide a convenient, relatively noninvasive source of tissue for examining Na(+)-H+ antiporter activity in human subjects.

Characterization of three human sec14p-like proteins: α-Tocopherol transport activity and expression pattern in tissues

Biochimie ◽  
2008 ◽  
Vol 90 (11-12) ◽  
pp. 1703-1715 ◽  
Author(s):  
Jean-Marc Zingg ◽  
Petra Kempna ◽  
Marcel Paris ◽  
Elke Reiter ◽  
Luis Villacorta ◽  
...  
Keyword(s):  
Expression Pattern ◽  
Transport Activity

scholarly journals A new model for Trypanosoma cruzi heme homeostasis depends on modulation of TcHTE protein expression

2020 ◽  
Vol 295 (38) ◽  
pp. 13202-13212
Author(s):  
Lucas Pagura ◽  
Evelyn Tevere ◽  
Marcelo L. Merli ◽  
Julia A. Cricco
Keyword(s):  
Trypanosoma Cruzi ◽  
De Novo ◽  
Mrna Levels ◽  
Biological Processes ◽  
Transport Activity ◽  
Critical Pathway ◽  
Heme Transport ◽  
Life Cycle Stages ◽  
Insight Into

Heme is an essential cofactor for many biological processes in aerobic organisms, which can synthesize it de novo through a conserved pathway. Trypanosoma cruzi, the etiological agent of Chagas disease, as well as other trypanosomatids relevant to human health, are heme auxotrophs, meaning they must import it from their mammalian hosts or insect vectors. However, how these species import and regulate heme levels is not fully defined yet. It is known that the membrane protein TcHTE is involved in T. cruzi heme transport, although its specific role remains unclear. In the present work, we studied endogenous TcHTE in the different life cycle stages of the parasite to gain insight into its function in heme transport and homeostasis. We have confirmed that TcHTE is predominantly detected in replicative stages (epimastigote and amastigote), in which heme transport activity was previously validated. We also showed that in epimastigotes, TcHTE protein and mRNA levels decrease in response to increments in heme concentration, confirming it as a member of the heme response gene family. Finally, we demonstrated that T. cruzi epimastigotes can sense intracellular heme by an unknown mechanism and regulate heme transport to adapt to changing conditions. Based on these results, we propose a model in which T. cruzi senses intracellular heme and regulates heme transport activity by adjusting the expression of TcHTE. The elucidation and characterization of heme transport and homeostasis will contribute to a better understanding of a critical pathway for T. cruzi biology allowing the identification of novel and essential proteins.

scholarly journals Reconstitution and characterization of ATP-dependent bile acid transport in human and rat placenta

1995 ◽  
Vol 311 (2) ◽  
pp. 479-485 ◽  
Author(s):  
P Bravo ◽  
J J G Marin ◽  
M J Beveridge ◽  
D A Novak
Keyword(s):  
Plasma Membrane ◽  
Bile Acid ◽  
Rat Liver ◽  
Brush Border ◽  
Atp Hydrolysis ◽  
Structural Characteristics ◽  
Acid Transport ◽  
Transport Activity ◽  
Canalicular Membrane

Bile acid (BA) transport across the human microvillus maternal-facing trophoblast plasma membrane (mTPM) has been recently reported to be stimulated by the presence of ATP [Marin, Bravo, El-Mir and Serrano (1993) J. Hepatol. 18, S41]. Reconstitution of BA transport activity in proteoliposomes from human mTPM is reported in this paper. Typical characteristics of BA transport in native mTPM vesicles, including a requirement for ATP hydrolysis and inhibition by other BA species, were preserved in proteoliposome preparations. BA transport into 20- and 14-day-gestation rat mTPM vesicles was also stimulated by the presence of ATP as noted in human mTPM and in the rat liver canalicular membrane. Besides this functional similarity, these ATP-dependent carriers may share structural characteristics, as demonstrated by studies using an antibody (100 Ab) raised against the 100 kDa BA carrier of the canalicular membrane from rat liver which recognized proteins in both human and rat brush-border trophoblast membranes.

scholarly journals SLC35A5 Protein—A Golgi Complex Member with Putative Nucleotide Sugar Transport Activity

2019 ◽  
Vol 20 (2) ◽  
pp. 276 ◽  
Author(s):  
Paulina Sosicka ◽  
Bożena Bazan ◽  
Dorota Maszczak-Seneczko ◽  
Yauhen Shauchuk ◽  
Teresa Olczak ◽  
...  
Keyword(s):  
Protein A ◽  
Sugar Transport ◽  
Uridine Diphosphate ◽  
Transport Activity ◽  
Nucleotide Sugar ◽  
Knock Out ◽  
Sugar Transporters ◽  
C Terminus ◽  
Glycolipid Synthesis ◽  
Galactose Transport

Solute carrier family 35 member A5 (SLC35A5) is a member of the SLC35A protein subfamily comprising nucleotide sugar transporters. However, the function of SLC35A5 is yet to be experimentally determined. In this study, we inactivated the SLC35A5 gene in the HepG2 cell line to study a potential role of this protein in glycosylation. Introduced modification affected neither N- nor O-glycans. There was also no influence of the gene knock-out on glycolipid synthesis. However, inactivation of the SLC35A5 gene caused a slight increase in the level of chondroitin sulfate proteoglycans. Moreover, inactivation of the SLC35A5 gene resulted in the decrease of the uridine diphosphate (UDP)-glucuronic acid, UDP-N-acetylglucosamine, and UDP-N-acetylgalactosamine Golgi uptake, with no influence on the UDP-galactose transport activity. Further studies demonstrated that SLC35A5 localized exclusively to the Golgi apparatus. Careful insight into the protein sequence revealed that the C-terminus of this protein is extremely acidic and contains distinctive motifs, namely DXEE, DXD, and DXXD. Our studies show that the C-terminus is directed toward the cytosol. We also demonstrated that SLC35A5 formed homomers, as well as heteromers with other members of the SLC35A protein subfamily. In conclusion, the SLC35A5 protein might be a Golgi-resident multiprotein complex member engaged in nucleotide sugar transport.

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