scholarly journals Cellular aspects of folate and antifolate membrane transport.

2000 ◽  
Vol 47 (3) ◽  
pp. 735-749 ◽  
Author(s):  
A Brzezińska ◽  
P Wińska ◽  
M Balińska
Keyword(s):  
Amino Acids ◽  
Membrane Transport ◽  
Physiological Role ◽  
Cancer Development ◽  
Transport Systems ◽  
Transport Activity ◽  
Neoplastic Cells ◽  
Folate Receptors

Folates--one carbon carriers--take part in the metabolism of purine, thymidylate and some amino acids. Internalization of these compounds employs several mechanisms of transport systems. Reduced folate carriers and folate receptors play the most important role in this process. The physiological role of these molecules in normal and neoplastic cells is described regarding changes in transport activity and connection of transport systems with resistance to antifolates and cancer development.

scholarly journals The Glycine- and Proline-Rich Protein AtGPRP3 Negatively Regulates Plant Growth in Arabidopsis

2020 ◽  
Vol 21 (17) ◽  
pp. 6168
Author(s):  
Xiaojing Liu ◽  
Xin Wang ◽  
Xin Yan ◽  
Shaobo Li ◽  
Hui Peng
Keyword(s):  
Amino Acids ◽  
Plant Growth ◽  
Physiological Role ◽  
Short Peptides ◽  
Hydrophobic Domain ◽  
Gfp Fusion Protein ◽  
Repeat Domain ◽  
Arabidopsis Plant ◽  
Proline Rich Protein

Glycine- and proline-rich proteins (GPRPs) comprise a small conserved family that is widely distributed in the plant kingdom. GPRPs are relatively short peptides (<200 amino acids) that contain three typical domains, including an N-terminal XYPP-repeat domain, a middle hydrophobic domain rich in alanine, and a C-terminal HGK-repeat domain. These proteins have been proposed to play fundamental roles in plant growth and environmental adaptation, but their functions remain unknown. In this study, we selected an Arabidopsis GPRP (AtGPRP3) to profile the physiological role of GPRPs. Transcripts of AtGPRP3 could be detected in the whole Arabidopsis plant, but greater amounts were found in the rosette, followed by the cauline. The AtGPRP3::GFP fusion protein was mainly localized in the nucleus. The overexpression and knockout of AtGPRP3, respectively, retarded and accelerated the growth of Arabidopsis seedlings, while the increase in the growth rate of atgprp3 plants was offset by the complementary expression of AtGPRP3. CAT2 and CAT3, but not CAT1, interacted with AtGPRP3 in the nuclei of Arabidopsis protoplasts. The knockout of CAT2 by CRISPR-Cas9 retarded the growth of the Arabidopsis seedlings. Together, our data suggest that AtGPRP3 negatively regulates plant growth, potentially through CAT2 and CAT3.

scholarly journals Key role of l-alanine in the control of hepatic protein synthesis

1987 ◽  
Vol 241 (2) ◽  
pp. 491-498 ◽  
Author(s):  
D Pérez-Sala ◽  
R Parrilla ◽  
M S Ayuso
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Physiological Role ◽  
Chain Elongation ◽  
Liver Protein ◽  
Isolated Liver Cells ◽  
Metabolic Transformation ◽  
Hepatic Protein Synthesis

We investigated the effects of administration of single amino acids to starved rats on the regulation of protein synthesis in the liver. Of all the amino acids tested, only alanine, ornithine and proline promoted statistically significant increases in the extent of hepatic polyribosome aggregation. The most effective of these was alanine, whose effect of promoting polyribosomal aggregation was accompanied by a decrease in the polypeptide-chain elongation time. The following observations indicate that alanine plays an important physiological role in the regulation of hepatic protein synthesis. Alanine was the amino acid showing the largest decrease in hepatic content in the transition from high (fed) to low (starved) rates of protein synthesis. The administration of glucose or pyruvate is also effective in increasing liver protein synthesis in starved rats, and their effects were accompanied by an increased hepatic alanine content. An increase in hepatic ornithine content does not lead to an increased protein synthesis, unless it is accompanied by an increase of alanine. The effect of alanine is observed either in vivo, in rats pretreated with cycloserine to prevent its transamination, or in isolated liver cells under conditions in which its metabolic transformation is fully impeded.

Response to osmotic stimuli in mesangial cells: role of system A transporter

1994 ◽  
Vol 267 (5) ◽  
pp. C1493-C1500 ◽  
Author(s):  
A. Yamauchi ◽  
A. Miyai ◽  
K. Yokoyama ◽  
T. Itoh ◽  
T. Kamada ◽  
...  
Keyword(s):  
Amino Acids ◽  
Mesangial Cells ◽  
Isobutyric Acid ◽  
Maximal Velocity ◽  
Transport Activity ◽  
Hypertonic Medium ◽  
Neutral Amino Acids ◽  
System A ◽  
Almost All

It has been suggested that mesangial cells have an osmoregulatory mechanism like that of renal medullary cells, such as intracellular accumulation of polyols in response to hypertonicity. We examined osmoregulatory role of neutral amino acids transported by system A in cultured mesangial cells. The contents of almost all amino acids increased under hypertonic conditions to more than twice the value in isotonic cells. In hypertonic cells, the system A transport activity, measured by Na(+)-dependent 2-(methylamino)isobutyric acid (MeAIB) uptake, was 3.8-fold the uptake in isotonic cells, reaching a maximum 16 h after the switch to hypertonic medium. The response to hypertonicity was the result of an increase in maximal velocity without change in Michaelis constant and was dependent on RNA and protein synthesis. When medium osmolality decreased from hypertonic to isotonic, MeAIB uptake reverted to the isotonic level within 16 h and a large transient efflux of L-proline occurred within 10 min. These results suggest that mesangial cells respond to extracellular hypertonicity by increasing system A transport activity and neutral amino acids can function as compatible osmolytes in mesangial cells.

The role of Na+ in membrane transport and respiration in the marine bacterium Deleya aesta 134

1991 ◽  
Vol 37 (6) ◽  
pp. 433-439 ◽  
Author(s):  
Marc Berthelet ◽  
Robert A. MacLeod
Keyword(s):  
Membrane Transport ◽  
Maximum Rate ◽  
Marine Bacterium ◽  
Transport Systems ◽  
Intact Cells ◽  
Effective Competition ◽  
Glucose Accumulation ◽  
Quinone Acceptor ◽  
The Relationship

Deleya aesta required Na+ for the uptake of 8 of 11 metabolites tested; the other three were transported at low rates in the absence of Na+ but at much higher rates in its presence. The optimal concentration of Na+ for maximum rate of transport of all the metabolites was 200 to 300 mM. Higher concentrations added as NaCl inhibited transport to the same extent as equiosomolar concentrations of other salts and sucrose. Li+ but not K+ could replace Na+ for the uptake of some metabolites but was only one-half as effective. Competition studies indicated that a number of different transport systems were involved in uptake. Inhibitor studies of succinate, L-alanine, and D-glucose accumulation (the last in both the presence and absence of Na+) suggested that for each a membrane potential was required. The relationship between rates of transport and oxidation of succinate by intact cells at various Na+ concentrations indicated that the Na+ requirement for oxidation reflected the Na+ requirement for transport. For D-glucose, the relationship was more complex, sinced over a narrow, low concentration range, Na+ inhibited respiration but not transport. Evidence for the presence in D. aesta 134 of a Na+-activated NADH–quinone acceptor oxidoreductase was obtained. Key words: Deleya aesta, marine bacteria, sodium, membrane transport, respiration.

scholarly journals Nitrite Transport Activity of the ABC-Type Cyanate Transporter of the Cyanobacterium Synechococcus elongatus

2009 ◽  
Vol 191 (10) ◽  
pp. 3265-3272 ◽  
Author(s):  
Shin-ichi Maeda ◽  
Tatsuo Omata
Keyword(s):  
Nitrogen Deficiency ◽  
Physiological Role ◽  
Synechococcus Elongatus ◽  
Transport Activity ◽  
High Affinity ◽  
Low Concentrations ◽  
Cyanobacterial Species ◽  
Relative Specificity ◽  
Nitrite Transport

ABSTRACT In addition to the ATP-binding cassette (ABC)-type nitrate/nitrite-bispecific transporter, which has a high affinity for both substrates (Km , ∼1 μM), Synechococcus elongatus has an active nitrite transport system with an apparent Km (NO2 −) value of 20 μM. We found that this activity depends on the cynABD genes, which encode a putative cyanate (NCO−) ABC-type transporter. Accordingly, nitrite transport by CynABD was competitively inhibited by NCO− with a Ki value of 0.025 μM. The transporter was induced under conditions of nitrogen deficiency, and the induced cells showed a V max value of 11 to 13 μmol/mg of chlorophyll per h for cyanate or nitrite, which could supply ∼30% of the amount of nitrogen required for optimum growth. Its relative specificity for the substrates and regulation at transcriptional and posttranslational levels suggested that the physiological role of the bispecific cyanate/nitrite transporter in S. elongatus is to allow nitrogen-deficient cells to assimilate low concentrations of cyanate in the medium. Its contribution to nitrite assimilation was significant in a mutant lacking the ABC-type nitrate/nitrite transporter, suggesting a possible role for CynABD in nitrite assimilation by cyanobacterial species that lack another high-affinity mechanism(s) for nitrite transport.

scholarly journals Effect of orally administered glutathione on glutathione levels in some organs of rats: role of specific transporters

1997 ◽  
Vol 78 (2) ◽  
pp. 293-300 ◽  
Author(s):  
Fabio Favilli ◽  
Patrizia Marraccini ◽  
Teresa Iantomasi ◽  
Maria T. Vincenzini
Keyword(s):  
Amino Acids ◽  
Oral Administration ◽  
Degradation Products ◽  
Specific Inhibitor ◽  
Buthionine Sulfoximine ◽  
Transport Systems ◽  
Rat Jejunum ◽  
Equivalent Amount ◽  
Specific Transport

The present study reports data on absorption of orally administered glutathione (GSH) in rat jejunum and in other organs, and the possible role of specific transport systems of GSH and γ-glutamyltranspeptidase (EC 2.3.2.1; γ-GT) activity. GSH levels were measured simultaneously in various organs after oral GSH administration to untreated rats and rats treated with L-buthionine sulfoximine (BSO) or acivicin (AT125). BSO selectively inhibits GSH intracellular synthesis and AT125 is a specific inhibitor of γ-GT activity. GSH levels were also measured after oral administration of an equivalent amount of the constituent amino acids of GSH to untreated and BSO-treated rats. Significant increases in GSH levels were found in jejunum, lung, heart, liver and brain after oral GSH administration to untreated rats. GSH increases were also obtained in all organs, except liver, when GSH was administered to rats previously GHS-depleted by treatment with BSO. The analysis of all results allowed us to distinguish between the increase in GSH intracellular levels due to intact GSH uptake by specific transporters, and that due to GSH degradation by γ-GT activity and subsequent absorption of degradation products with intracellular resynthesis of GSH; both these mechanisms seemed to be involved in increasing GSH content in heart after oral GSH administration. Jejunum, lung and brain took up GSH mostly intact, by specific transport systems, while in liver GSH uptake occurred only by its breakdown by γ-GT activity followed by intracellular resynthesis.

scholarly journals Fate of uptaken host proteins in Taenia solium and Taenia crassiceps cysticerci

2018 ◽  
Vol 38 (4) ◽  
Author(s):  
Jeanette Flores-Bautista ◽  
José Navarrete-Perea ◽  
Gladis Fragoso ◽  
Ana Flisser ◽  
Xavier Soberón ◽  
...  
Keyword(s):  
Amino Acids ◽  
Culture Medium ◽  
Taenia Solium ◽  
Physiological Role ◽  
Essential Amino Acids ◽  
Host Proteins ◽  
Taenia Crassiceps ◽  
The Matrix ◽  
Host Parasite

During the study of host–parasite relationships in taeniid parasite diseases, including cysticercosis and hydatidosis, reports have described the presence of host proteins in the cyst fluid and tissue of metacestodes. However, the fate or role of host elements inside the parasite remains barely explored. After the publication of genomes of four cestode species, it became clear that these organisms possess a limited biosynthetic capability. The initial goal of the present study was to determine if uptaken host proteins could be a source of essential amino acids for cysticerci. To track the utilization of uptaken proteins, we added metabolically labeled IgG-3H and GFP-3H to the culture medium of Taenia crassiceps cysticerci. Incorporation of labeled amino acid was evaluated by fluorography in cysticerci extracts. Our results showed that the use of uptaken proteins by cysticerci as a source of amino acids appeared negligible. Exploring alternative fates for the host proteins, proteomic analysis of the protein matrix in calcareous corpuscles was carried out. Since T. crassiceps does not contain calcareous corpuscles, proteomic analyses were performed in corpuscles of Taenia solium cysticerci. Our results demonstrated that host proteins represented approximately 70% of protein content in the calcareous corpuscles. The presence of the two major uptaken host proteins, namely albumin and IgG, was also demonstrated by Western blot in the matrix of corpuscles. Our findings strongly suggested that the uptake and disposal of host proteins involve calcareous corpuscles, expanding the physiological role of these mineral concretions to a far more important level than previously proposed.

scholarly journals Effect of pentagastrin and gastrin-17 on the secretory function of the gastric glands

2022 ◽  
pp. 75-78
Author(s):  
M. A. Zhuraeva ◽  
V. A. Aleynik ◽  
N. D. Ashuralieva ◽  
D. S. Kholikova
Keyword(s):  
Amino Acids ◽  
Physiological Role ◽  
The Body ◽  
Short Chain ◽  
Molecular Forms ◽  
Secretory Function ◽  
Gastric Glands ◽  
Digestive Glands

The regulation of the digestive glands of the stomach and pancreas in the body of animals and humans is provided by peptides, most of which are in various molecular forms. 10 molecular forms of peptides of the gastrin group and 5 peptides of the cholecystokinin (CCK) group have been identified, containing in their structure from 4 to 56 amino acids, the physiological role of which has been little studied. It has been proven that the liver removes up to 85% of short-chain peptides of the gastrin (pentagastrin) and cholecystokinin (CCK-8) groups.

Physiological role of tyrosine transport systems in Halobacterium salinarium

1994 ◽  
Vol 162 (1-2) ◽  
pp. 126-130 ◽  
Author(s):  
L. B. Lobyreva ◽  
M. V. Kokoeva ◽  
V. K. Plakunov
Keyword(s):  
Physiological Role ◽  
Transport Systems ◽  
Halobacterium Salinarium
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