Genomic analysis of nucleoside transporters in Diptera and functional characterization of DmENT2, a Drosophila equilibrative nucleoside transporter

2007 ◽  
Vol 28 (3) ◽  
pp. 337-347 ◽  
Author(s):  
Jerry Machado ◽  
Parween Abdulla ◽  
W. J. Brad Hanna ◽  
Arthur J. Hilliker ◽  
Imogen R. Coe
Keyword(s):  
Sequence Similarity ◽  
Functional Characterization ◽  
Genomic Analysis ◽  
Structure And Function ◽  
Nucleoside Transporters ◽  
Nucleoside Transport ◽  
Nucleoside Transporter ◽  
Nucleoside Transport Inhibitors ◽  
And Function

The recent completion of genome sequencing projects in a number of eukaryotes allows comparative analysis of orthologs, which can aid in identifying evolutionary constraints on protein structure and function. Nucleoside transporters (NTs) are present in a diverse array of organisms and previous studies have suggested that there is low protein sequence similarity but conserved structure in invertebrate and vertebrate NT orthologs. In addition, most taxa possess multiple NT isoforms but their respective roles in the physiology of the organism are not clear. To investigate the evolution of the structure and function of NTs, we have extended our previous studies by identifying NT orthologs in the Dipteran Anopheles gambiae and comparing these proteins to human and Drosophila melanogaster (Dm) NTs. In addition, we have functionally characterized DmENT2, one of three putative D. melanogaster ENTs that we have previously described. DmENT2 has broad substrate specificity, is insensitive to standard nucleoside transport inhibitors and is expressed in the digestive tract of late stage embryos based on in situ hybridization. DmENT1 and DmENT2 are expressed in most stages during development with the exception of early embryogenesis suggesting specific physiological roles for each isoform. These data represent the first complete genomic analysis of Dipteran NTs and the first report of the functional characterization of any Dipteran NT.

scholarly journals Functional Characterization of Novel Human and Mouse Equilibrative Nucleoside Transporters (hENT3 and mENT3) Located in Intracellular Membranes

2005 ◽  
Vol 280 (16) ◽  
pp. 15880-15887 ◽  
Author(s):  
Stephen A. Baldwin ◽  
Sylvia Y. M. Yao ◽  
Ralph J. Hyde ◽  
Amy M. L. Ng ◽  
Sophie Foppolo ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Functional Characterization ◽  
Human Cells ◽  
Nucleoside Transporters ◽  
Nucleoside Transport ◽  
Nucleoside Transporter ◽  
Transport Activity ◽  
Transporter Family ◽  
Human And Mouse

The first mammalian examples of the equilibrative nucleoside transporter family to be characterized, hENT1 and hENT2, were passive transporters located predominantly in the plasma membranes of human cells. We now report the functional characterization of members of a third subgroup of the family, from human and mouse, which differ profoundly in their properties from previously characterized mammalian nucleoside transporters. The 475-residue human and mouse proteins, designated hENT3 and mENT3, respectively, are 73% identical in amino acid sequence and possess long N-terminal hydrophilic domains that bear typical (DE)XXXL(LI) endosomal/lysosomal targeting motifs. ENT3 transcripts and proteins are widely distributed in human and rodent tissues, with a particular abundance in placenta. However, in contrast to ENT1 and ENT2, the endogenous and green fluorescent protein-tagged forms of the full-length hENT3 protein were found to be predominantly intracellular proteins that co-localized, in part, with lysosomal markers in cultured human cells. Truncation of the hydrophilic N-terminal region or mutation of its dileucine motif to alanine caused the protein to be relocated to the cell surface both in human cells and inXenopusoocytes, allowing characterization of its transport activity in the latter. The protein proved to be a broad selectivity, low affinity nucleoside transporter that could also transport adenine. Transport activity was relatively insensitive to the classical nucleoside transport inhibitors nitrobenzylthioinosine, dipyridamole, and dilazep and was sodium ion-independent. However, it was strongly dependent upon pH, and the optimum pH value of 5.5 probably reflected the location of the transporter in acidic, intracellular compartments.

scholarly journals [3H]dipyridamole binding to nucleoside transporters from guinea-pig and rat lung

1986 ◽  
Vol 240 (3) ◽  
pp. 879-883 ◽  
Author(s):  
M M Shi ◽  
J D Young
Keyword(s):  
Guinea Pig ◽  
Nucleoside Transporters ◽  
Nucleoside Transport ◽  
Affinity Binding ◽  
Nucleoside Transporter ◽  
High Affinity Binding ◽  
High Affinity ◽  
Nucleoside Transport Inhibitors ◽  
Transport Inhibitors ◽  
Low Sensitivity

Membranes from guinea-pig lung exhibited high-affinity binding of [3H]dipyridamole, a potent inhibitor of nucleoside transport. Binding (apparent KD 2 nM) was inhibited by the nucleoside-transport inhibitors nitrobenzylthioinosine (NBMPR), dilazep and lidoflazine and by the transported nucleosides uridine and adenosine. In contrast, there was no detectable high-affinity binding of [3H]dipyridamole to lung membranes from the rat, a species whose nucleoside transporters exhibit a low sensitivity to dipyridamole inhibition. Bmax. values for high-affinity binding of [3H]dipyridamole and [3H]NBMPR to guinea-pig membranes were similar, suggesting that these structurally unrelated ligands bind to the NBMPR-sensitive nucleoside transporter with the same stoichiometry.

Functional characterization of human brown adipose tissue metabolism

2020 ◽  
Vol 477 (7) ◽  
pp. 1261-1286 ◽  
Author(s):  
Marie Anne Richard ◽  
Hannah Pallubinsky ◽  
Denis P. Blondin
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Functional Characterization ◽  
Human Infants ◽  
Positron Emission ◽  
Brown Adipose ◽  
Treatment Of Obesity ◽  
And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

scholarly journals A Rubisco-binding protein is required for normal pyrenoid number and starch sheath morphology inChlamydomonas reinhardtii

2019 ◽  
Vol 116 (37) ◽  
pp. 18445-18454 ◽  
Author(s):  
Alan K. Itakura ◽  
Kher Xing Chan ◽  
Nicky Atkinson ◽  
Leif Pallesen ◽  
Lianyong Wang ◽  
...  
Keyword(s):  
Surface Area ◽  
Structure And Function ◽  
Binding Motif ◽  
Starch Granules ◽  
Wild Type ◽  
Bisphosphate Carboxylase ◽  
Biophysical Mechanism ◽  
Mechanism Function ◽  
And Function

A phase-separated, liquid-like organelle called the pyrenoid mediates CO2fixation in the chloroplasts of nearly all eukaryotic algae. While most algae have 1 pyrenoid per chloroplast, here we describe a mutant in the model algaChlamydomonasthat has on average 10 pyrenoids per chloroplast. Characterization of the mutant leads us to propose a model where multiple pyrenoids are favored by an increase in the surface area of the starch sheath that surrounds and binds to the liquid-like pyrenoid matrix. We find that the mutant’s phenotypes are due to disruption of a gene, which we call StArch Granules Abnormal 1 (SAGA1) because starch sheath granules, or plates, in mutants lacking SAGA1 are more elongated and thinner than those of wild type. SAGA1 contains a starch binding motif, suggesting that it may directly regulate starch sheath morphology. SAGA1 localizes to multiple puncta and streaks in the pyrenoid and physically interacts with the small and large subunits of the carbon-fixing enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), a major component of the liquid-like pyrenoid matrix. Our findings suggest a biophysical mechanism by which starch sheath morphology affects pyrenoid number and CO2-concentrating mechanism function, advancing our understanding of the structure and function of this biogeochemically important organelle. More broadly, we propose that the number of phase-separated organelles can be regulated by imposing constraints on their surface area.

scholarly journals Characterization of splice variants of human caspase-activated DNase with CIDE-N structure and function

FEBS Letters ◽  
2004 ◽  
Vol 566 (1-3) ◽  
pp. 234-240 ◽  
Author(s):  
José R. Bayascas ◽  
Vı́ctor J. Yuste ◽  
Carme Solé ◽  
Isabel Sánchez-López ◽  
Miquel F. Segura ◽  
...  
Keyword(s):  
Splice Variants ◽  
Structure And Function ◽  
Caspase Activated Dnase ◽  
And Function ◽  
Human Caspase
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