Na(+)-independent transport (uniport) of amino acids and glucose in mammalian cells.

1994 ◽  
Vol 196 (1) ◽  
pp. 93-108
Author(s):  
D K Kakuda ◽  
C L MacLeod
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Mammalian Cells ◽  
Glucose Transporter ◽  
Sequence Similarity ◽  
Amino Acid Sequence Similarity ◽  
Amino Acid Transporters ◽  
Cationic Amino Acid ◽  
Transporter Family ◽  
Share Amino Acid Sequence

Recent advances have made possible the isolation of the genes and their cDNAs encoding Na(+)-independent amino acid transporters. Two classes of amino acid 'uniporters' have been isolated. One class contains the mCAT (murine cationic amino acid transporter) gene family that encodes proteins predicted to span the membrane 12-14 times and exhibits structural properties similar to the GLUT (glucose transporter) family and to other well-known transporters. The other class consists of two known genes, rBAT (related to B system amino acid transporters) and 4F2hc, that share amino acid sequence similarity with alpha-amylases and alpha-glucosidases. They are type II glycoproteins predicted to span the membrane only once, yet they mediate the Na(+)-independent transport of cationic and zwitterionic amino acids in Xenopus oocytes. Mutations in the human rBAT gene have been identified by Palacín and his co-workers in several families suffering from a heritable form of cystinuria. This important finding clearly establishes a key role for rBAT in cystine transport. The two classes of amino acid transporters are compared with the well-studied GLUT family of Na(+)-independent glucose transporters.

scholarly journals Site-directed mutagenesis at aspartate and glutamate residues of xylanase from Bacillus pumilus

1992 ◽  
Vol 288 (1) ◽  
pp. 117-121 ◽  
Author(s):  
E P Ko ◽  
H Akatsuka ◽  
H Moriyama ◽  
A Shinmyo ◽  
Y Hata ◽  
...  
Keyword(s):  
Amino Acids ◽  
Reaction Mechanism ◽  
Amino Acid ◽  
Bacillus Pumilus ◽  
Specific Activity ◽  
Sequence Similarity ◽  
Site Directed Mutagenesis ◽  
Dimensional Structure ◽  
Amino Acid Sequence Similarity ◽  
Directed Mutagenesis

To elucidate the reaction mechanism of xylanase, the identification of amino acids essential for its catalysis is of importance. Studies have indicated the possibility that the reaction mechanism of xylanase is similar to that of hen's egg lysozyme, which involves acidic amino acid residues. On the basis of this assumption, together with the three-dimensional structure of Bacillus pumilus xylanase and its amino acid sequence similarity to other xylanases of different origins, three acidic amino acids, namely Asp-21, Glu-93 and Glu-182, were selected for site-directed mutagenesis. The Asp residue was altered to either Ser or Glu, and the Glu residues to Ser or Asp. The purified mutant xylanases D21E, D21S, E93D, E93S, E182D and E182S showed single protein bands of about 26 kDa on SDS/PAGE. C.d. spectra of these mutant enzymes show no effect on the secondary structure of xylanase, except that of D21E, which shows a little variation. Furthermore, mutations of Glu-93 and Glu-182 resulted in a drastic decrease in the specific activity of xylanase as compared with mutation of Asp-21. On the basis of these results we propose that Glu-93 and Glu-182 are the best candidates for the essential catalytic residues of xylanase.

scholarly journals The heterodimeric amino acid transporter 4F2hc/y+LAT2 mediates arginine efflux in exchange with glutamine

2000 ◽  
Vol 349 (3) ◽  
pp. 787-795 ◽  
Author(s):  
Angelika BRÖER ◽  
Carsten A. WAGNER ◽  
Florian LANG ◽  
Stefan BRÖER
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Mammalian Cells ◽  
Substrate Inhibition ◽  
Cell Types ◽  
Xenopus Laevis Oocytes ◽  
Cationic Amino Acid ◽  
New Family ◽  
Arginine Uptake ◽  
Intracellular Binding

The cationic amino acid arginine, due to its positive charge, is usually accumulated in the cytosol. Nevertheless, arginine has to be released by a number of cell types, e.g. kidney cells, which supply other organs with this amino acid, or the endothelial cells of the blood–brain barrier which release arginine into the brain. Arginine release in mammalian cells can be mediated by two different transporters, y+LAT1 and y+LAT2. For insertion into the plasma membrane, these transporters have to be associated with the type-II membrane glycoprotein 4F2hc [Torrents, Estevez, Pineda, Fernandez, Lloberas, Shi, Zorzano and Palacin (1998) J. Biol. Chem. 273, 32437–32445]. The present study elucidates the function and distribution of y+LAT2. In contrast to y+LAT1, which is expressed mainly in kidney epithelial cells, lung and leucocytes, y+LAT2 has a wider tissue distribution, including brain, heart, testis, kidney, small intestine and parotis. When co-expressed with 4F2hc in Xenopus laevis oocytes, y+LAT2 mediated uptake of arginine, leucine and glutamine. Arginine uptake was inhibited strongly by lysine, glutamate, leucine, glutamine, methionine and histidine. Mutual inhibition was observed when leucine or glutamine was used as substrate. Inhibition of arginine uptake by neutral amino acids depended on the presence of Na+, which is a hallmark of y+LAT-type transporters. Although arginine transport was inhibited strongly by glutamate, this anionic amino acid was only weakly transported by 4F2hc/y+LAT2. Amino acid transport via 4F2hc/y+LAT2 followed an antiport mechanism similar to the other members of this new family. Only preloaded arginine could be released in exchange for extracellular amino acids, whereas marginal release of glutamine or leucine was observed under identical conditions. These results indicated that arginine has the highest affinity for the intracellular binding site and that arginine release may be the main physiological function of this transporter.

The role of amino acid transporters in inherited and acquired diseases

2011 ◽  
Vol 436 (2) ◽  
pp. 193-211 ◽  
Author(s):  
Stefan Bröer ◽  
Manuel Palacín
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Mammalian Cells ◽  
Neuronal Excitability ◽  
Tumour Progression ◽  
Building Blocks ◽  
Amino Acid Uptake ◽  
Whole Body ◽  
Amino Acid Transporters ◽  
Acid Uptake

Amino acids are essential building blocks of all mammalian cells. In addition to their role in protein synthesis, amino acids play an important role as energy fuels, precursors for a variety of metabolites and as signalling molecules. Disorders associated with the malfunction of amino acid transporters reflect the variety of roles that they fulfil in human physiology. Mutations of brain amino acid transporters affect neuronal excitability. Mutations of renal and intestinal amino acid transporters affect whole-body homoeostasis, resulting in malabsorption and renal problems. Amino acid transporters that are integral parts of metabolic pathways reduce the function of these pathways. Finally, amino acid uptake is essential for cell growth, thereby explaining their role in tumour progression. The present review summarizes the involvement of amino acid transporters in these roles as illustrated by diseases resulting from transporter malfunction.

scholarly journals Supplemental leucine and isoleucine affect expression of cationic amino acid transporters and myosin, serum concentration of amino acids, and growth performance of pigs

2013 ◽  
Vol 12 (1) ◽  
pp. 115-126 ◽  
Author(s):  
M. Cervantes-Ramírez ◽  
V. Mendez-Trujillo ◽  
B.A. Araiza-Piña ◽  
M.A. Barrera-Silva ◽  
D. González-Mendoza ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Serum Concentration ◽  
Growth Performance ◽  
Amino Acid Transporters ◽  
Cationic Amino Acid ◽  
Affect Expression

scholarly journals T-kininogenase activity of the rat submandibular gland is predominantly due to the kallikrein-like serine protease antigen γ

1991 ◽  
Vol 280 (1) ◽  
pp. 19-25 ◽  
Author(s):  
T Berg ◽  
I Wassdal ◽  
T Mindroiu ◽  
K Sletten ◽  
G Scicli ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Molecular Mass ◽  
Submandibular Gland ◽  
Sequence Similarity ◽  
Rat Plasma ◽  
Amino Acid Sequence Similarity ◽  
Tissue Kallikrein ◽  
Reverse Phase ◽  
Rat Submandibular Gland

T-kininogen, the major kininogen in rat plasma, releases Ile-Ser-bradykinin (T-kinin) when incubated with trypsin, but is not a substrate for tissue kallikrein. Enzymes able to release T-kinins from T-kininogen have been found in the rat submandibular gland, but precise identification of these enzymes and their possible relationship to kallikrein-like enzymes has not been established. We studied T-kininogenase activity in fractionated submandibular gland homogenate. The main T-kininogen catalytic enzyme was purified and characterized, and found to be identical to antigen gamma, a kallikrein-like enzyme which we have previously characterized. Of other identified kallikrein-like enzymes only tonin showed weak T-kininogenase activity, which was about 0.25% of that of antigen gamma. No other T-kininogen catalytic enzymes were observed. Antigen gamma released a kinin which was identified as T-kinin by reverse-phase h.p.l.c. The T-kininogenase activity of antigen gamma had a Km of 29 +/- 4 microM and a kcat/Km of 140 M-1.s-1, and was comparable with its high and low molecular mass-kininogenase activity (7.4 and 10 micrograms of kinin/h per mg respectively). In contrast, tissue kallikrein released 0.2 and 42,200 micrograms of kinin/h per mg respectively. Thus antigen gamma is a weak kininogenase. The isoelectric point of antigen gamma, but not its molecular mass, differed from that of other kallikrein-like enzymes. Isoelectrofocusing in flat-bed gels combined with immunostaining was therefore a convenient method for identification. The kallikrein-like nature of antigen gamma was demonstrated by its immunological similarity to tissue kallikrein and tonin and by 91% and 87% amino acid sequence similarity with tonin and kallikrein respectively (67 amino acids sequenced). Complete identity was also not observed with other sequenced kallikrein genes, mRNAs or proteins.

scholarly journals Nonstructural p26 proteins encoded by the 3’-proximal genes of velariviruses and criniviruses are orthologs

2019 ◽  
Vol 165 (2) ◽  
pp. 439-443
Author(s):  
I. B. Rogozin ◽  
A. A. Agranovsky
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Sequence Similarity ◽  
Structural Proteins ◽  
Amino Acid Sequence Similarity ◽  
High Plasticity ◽  
Amino Acid Sequence Alignment ◽  
Bioinformatic Tools ◽  
The Family ◽  
Share Amino Acid Sequence

AbstractThe 3’-most genes in RNA-2 of the Crinivirus genus members (family Closteroviridae) code for non-structural p26 proteins that share amino acid sequence similarity [Stewart LR, Hwang MS, Falk BW (2009) Virus Res 145:293-299]. In this study, sensitive bioinformatic tools have been used to identify the homologous p26 proteins encoded by the 3’ genes in monopartite genomes of the members of Velarivirus, another Closteroviridae genus, and mint vein banding-associated virus, an unassigned member of the family. The p26 proteins showed similarity in their predicted secondary structures, but an amino acid sequence alignment showed no strictly conserved positions, thus indicating a high plasticity of these non-structural proteins. The implications of the sequence analysis for possible functions of the crinivirus and velarivirus p26 proteins are discussed.

scholarly journals Characterization of the avian GLUT1 glucose transporter: differential regulation of GLUT1 and GLUT3 in chicken embryo fibroblasts.

1995 ◽  
Vol 6 (11) ◽  
pp. 1575-1589 ◽  
Author(s):  
P Wagstaff ◽  
H Y Kang ◽  
D Mylott ◽  
P J Robbins ◽  
M K White
Keyword(s):  
Glucose Transport ◽  
Chicken Embryo ◽  
Mammalian Cells ◽  
Glucose Transporter ◽  
Sequence Similarity ◽  
Tumor Promoter ◽  
Amino Acid Sequence Similarity ◽  
Embryo Fibroblasts ◽  
Chicken Embryo Fibroblasts ◽  
Glut1 Glucose Transporter

Vertebrate cells that are transformed by oncogenes such as v-src or are stimulated by mitogens have increased rates of glucose uptake. In rodent cells, the mechanisms whereby glucose transport is up-regulated are well understood. Stimulation of glucose transport involves an elevation in mRNA encoding the GLUT1 glucose transporter that is controlled at the levels of both transcription and mRNA stability. Cloning and sequencing of chicken GLUT1 cDNA showed that it shares 95% amino acid sequence similarity to mammalian GLUT1s. Nevertheless, unlike mammalian GLUT1 mRNA, it was not induced by v-src, serum addition, or treatment with the tumor promoter 12-O-tetradecanoylphorbol 13-acetate in chicken embryo fibroblasts. Rather, the induction of glucose transport in chicken embryo fibroblasts by v-src, serum, and 12-O-tetradecanoylphorbol 13-acetate was associated with induction of GLUT3 mRNA level and GLUT3 transcription. Rat fibroblasts were also found to express both GLUT1 and GLUT3 isoforms, but v-src induced GLUT1 and not GLUT3. This suggests that animal cells require both a basal and an upregulatable glucose transporter and that these functions have been subsumed by different GLUT isoforms in avian and mammalian cells.

Molecular Characterization of a New Lectin from the Marine Alga Ulva pertusa

2004 ◽  
Vol 36 (2) ◽  
pp. 111-117 ◽  
Author(s):  
Sheng Wang ◽  
Fu-Di Zhong ◽  
Yong-Jiang Zhang ◽  
Zu-Jian Wu ◽  
Qi-Ying Lin ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Divalent Cations ◽  
Sequence Similarity ◽  
Ulva Pertusa ◽  
Amino Acid Sequence Similarity ◽  
Degenerate Primers ◽  
Heat Stable ◽  
Rapid Amplification

Abstract A new lectin, named UPL1, was purified from a green alga Ulva pertusa by an affinity chromatography on the bovine-thyroglobulin-Sepharose 4B column. The molecular mass of the algal lectin was about 23 kD by SDS-PAGE, and it specifically agglutinated rabbit erythrocytes. The hemagglutinating activity for rabbit erythrocytes could be inhibited by bovine thyroglobulin and N-acetyl-D-glucosamine. The lectin UPL1 required divalent cations for maintenance of its biological activity, and was heat-stable, and had higher activity within pH 6–8. The N-terminal amino acid sequence of the purified lectin was determined (P83209) and a set of degenerate primers were designed. The full-length cDNA of the lectin was cloned by rapid amplification of cDNA ends (RACE) method (AY433960). Sequence analysis of upl1 indicated it was 1084 bp long, and encoded a premature protein of 203 amino acids. The N-terminal sequence of the mature UPL1 polypeptide started at amino acid 54 of the deduced sequence from the cDNA, indicating 53 amino acids lost due to posttranslational modification. The primary structure of the Ulva pertusa lectin did not show amino acid sequence similarity with known plant and animal lectins. Hence, this protein may be the paradigm of a novel lectin family.

scholarly journals System-L amino acid transporters play a key role in pancreatic β-cell signalling and function

2016 ◽  
Vol 56 (3) ◽  
pp. 175-187 ◽  
Author(s):  
Qi Cheng ◽  
Violeta D Beltran ◽  
Stanley M H Chan ◽  
Jeremy R Brown ◽  
Alan Bevington ◽  
...  
Keyword(s):  
Amino Acids ◽  
Insulin Secretion ◽  
Amino Acid ◽  
Mammalian Cells ◽  
Critical Role ◽  
Cell Signalling ◽  
Amino Acid Transporters ◽  
Β Cell ◽  
System L ◽  
And Function

Abstract The branched-chain amino acids (BCAA) leucine, isoleucine and valine, are essential amino acids that play a critical role in cellular signalling and metabolism. They acutely stimulate insulin secretion and activate the regulatory serine/threonine kinase mammalian target of rapamycin complex 1 (mTORC1), a kinase that promotes increased β-cell mass and function. The effects of BCAA on cellular function are dependent on their active transport into the mammalian cells via amino acid transporters and thus the expression and activity of these transporters likely influence β-cell signalling and function. In this report, we show that the System-L transporters are required for BCAA uptake into clonal β-cell lines and pancreatic islets, and that these are essential for signalling to mTORC1. Further investigation revealed that the System-L amino acid transporter 1 (LAT1) is abundantly expressed in the islets, and that knockdown of LAT1 using siRNA inhibits mTORC1 signalling, leucine-stimulated insulin secretion and islet cell proliferation. In summary, we show that the LAT1 is required for regulating β-cell signalling and function in islets and thus may be a novel pharmacological/nutritional target for the treatment and prevention of type 2 diabetes.

Transporters for Cationic Amino Acids in Animal Cells: Discovery, Structure, and Function

1998 ◽  
Vol 78 (2) ◽  
pp. 487-545 ◽  
Author(s):  
R. DEVÉS ◽  
C. A. R. BOYD
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Structure And Function ◽  
Xenopus Laevis Oocytes ◽  
Amino Acid Transporters ◽  
Cdna Clones ◽  
Animal Cells ◽  
Cationic Amino Acid ◽  
Cationic Amino Acids ◽  
And Function

Devés, R., and C. A. R. Boyd. Transporters for Cationic Amino Acids in Animal Cells: Discovery, Structure, and Function. Physiol. Rev. 78: 487–545, 1998. — The structure and function of the four cationic amino acid transporters identified in animal cells are discussed. The systems differ in specificity, cation dependence, and physiological role. One of them, system y+, is selective for cationic amino acids, whereas the others (B0,+, b0,+, and y+L) also accept neutral amino acids. In recent years, cDNA clones related to these activities have been isolated. Thus two families of proteins have been identified: 1) CAT or cationic amino acid transporters and 2) BAT or broad-scope transport proteins. In the CAT family, three genes encode for four different isoforms [CAT-1, CAT-2A, CAT-2(B) and CAT-3]; these are ∼70-kDa proteins with multiple transmembrane segments ( 12 – 14 ), and despite their structural similarity, they differ in tissue distribution, kinetics, and regulatory properties. System y+is the expression of the activity of CAT transporters. The BAT family includes two isoforms (rBAT and 4F2hc); these are 59- to 78-kDa proteins with one to four membrane-spanning segments, and it has been proposed that these proteins act as transport regulators. The expression of rBAT and 4F2hc induces system b0,+and system y+L activity in Xenopus laevis oocytes, respectively. The roles of these transporters in nutrition, endocrinology, nitric oxide biology, and immunology, as well as in the genetic diseases cystinuria and lysinuric protein intolerance, are reviewed. Experimental strategies, which can be used in the kinetic characterization of coexpressed transporters, are also discussed.

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