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Results for “Protein transport”

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At least 19 recordsLinked to original sources
PubMed1977

Similar polypeptide composition of fast-transported proteins in rat motor and sensory axons.

SDS-polyacrylamide gel electrophoresis was used to characterize labeled proteins transported in rat motor and sensory axons after application of 3H-leucine to the neuron cell bodies. Two types of experiments were performed: first, transported protein accumulating proximal to a ligature placed on the sciatic nerve was analyzed; second, the segment of sciatic nerve nearest to the "wavecrest" of transported protein travelling down the nerve was analyzed. In both cases, no significant differences in peak position or amplitude were found in gels containing labeled proteins from motor or sensory axons. This may mean that the majority of fast-transported protein is involved in an axonal function common to the two types of neuron.

Animals↗
PubMed1977

Binding properties of serum vitamin D transport proteins in vertebrates for 24R, 25-dihydroxycholecalciferol and 24S, 25-dihydroxycholecalciferol in vitro.

1. The affinities of the specific vitamin D plasma transport proteins for 25-hydroxycholecalciferol, 24R, 25-dihydroxycholecalciferol and 24S, 25-dihydroxycholecalciferol were studied in 34 vertebrate species. 2. Fish plasma proteins bound 25-hydroxycholecalciferol, 24R, 25-dihydroxycholecalciferol and 24S, 25-dihydroxycholecalciferol with equal efficiency. 3. Vitamin D transport proteins in birds and a monotreme bound 25-hydroxycholecalciferol more efficiently than 24R, 25-dihydroxycholecalciferol; in one bird the two seco-steroids were bound with equal efficiency. 4. Transport proteins from marsupial and placental mammals bound 24R, 25-dihydroxycholecalciferol more efficiently than 24S, 25-dihydroxycholecalciferol. 5. Twelve mammal transport proteins bound 25-hydroxycholecalciferol and 24R, 25-dihydroxycholecalciferol with equal efficiency, however, in six mammals 25-hydroxycholecalciferol was more efficiently bound.

24,25-Dihydroxyvitamin D 3↗
PubMed1979

The anion-transport protein of the human erythrocyte membrane. Studies on fragments produced by pepsin digestion.

We have studied the fragmentation by pepsin in 1 M-acetic acid of the erythrocyte anion-transport protein in erythrocyte membranes. The location of the fragments obtained was determined by radioiodinating the protein with the use of lactoperoxidase, and identifying the labelled peptides obtained in peptide "maps" of thermolysin digests of the fragments. Three of the fragments were found to be related overlapping products, and shared a common C-terminus. The major site of pepsin cleavage leading to the C-termini of these fragments was shown to be close to the major site of extracellular cleavage of the protein by proteinases active at a neutral pH. Another two fragments were isolated and shown to be derived from the C-terminal portion of the protein. No well-defined large radioactive fragments of the protein were solubilized from the membrane by pepsin in 1 M-acetic acid, the bulk of the radioactivity attributable to the anion transport protein being recovered in very small fragments that could not be resolved by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Our results suggest that the polypeptide chain of the anion-transport protein emerges at the extracellular face of the membrane 8000-13000 daltons on the N-terminal side of the major site of extracellular cleavage of the protein by proteinases that are active at a neutral pH.

Amino Acid Sequence↗
PubMed1978

Glucose binding and transport proteins extracted from fast-growing chicken fibroblasts.

Preconfluent or confluent fibroblasts grown in 5% serum medium yielded, without cell lysis, all the glucose-binding protein and most of the transport-stimulating activity in the cell wash fluid obtained with a 10 mM sodium octanoate-containing solution. For assay, octanoate was removed, and after the binding protein was labeled with [(14)C]glucose, the factors were chromatographed on Sephadex G-200 and the transport-stimulating and factor-bound [(14)C]glucose activities were measured. Three peaks were separated, which more or less overlapped for both functions; upon chromatography on DEAE-cellulose, these peaks yielded overlapping or separate peaks for the two functions, presumably indicating their separability. Serum, when similarly chromatographed, showed only peaks for transport which, with the exception of one major peak with both functions, more or less overlapped with those from the wash fluid. Glucose transport rates, when compared in fibroblasts grown in glucose and in fructose and in Rous sarcoma virus-transformed cells grown in glucose, were in the proportion of 1:3.7:6.3. Addition of extracted transport protein stimulated the transport of both the glucose-grown and fructose-grown normal cells but showed no effect on the transport of transformed cells. Addition of transport protein induced the formation of [(14)C]deoxyglucose 6-phosphate in amounts proportional to the increased transport of [(14)C]deoxyglucose into fibroblasts. On sodium dodecyl sulfate electrophoresis, using the tightly bound [(14)C]glucose for assay, purified binding protein yielded large fractions of 36,000 and 18,000 and small ones of 55,000 and 73,000 daltons; the 18,000-dalton fraction is supposedly the monomeric form of the binding protein.

Animals↗
PubMed2026

Genome-wide characterization of the sugar transporter protein family identifies candidate genes for bacterial wilt resistance breeding in tobacco.

Sugar transporter proteins (STPs) play pivotal roles in hexose allocation and plant stress responses. However, systematic characterization of the STP family in tobacco (Nicotiana tabacum) and its involvement in Ralstonia solanacearum resistance remains unclear. In this study, 37 NtSTP genes were identified and classified into six groups, with Group VI being the most conserved and Group V exhibiting dicot-specific expansion. Gene structure and conserved motif analyses revealed that most NtSTP members possess the typical MFS_STP domain, although variations in exon-intron organization and motif composition suggested functional divergence. Tandem duplication (TD) served as the primary driver of NtSTP family expansion, and Ka/Ks values of all paralogous pairs were less than 1, indicative of purifying selection. Promoter cis-element analysis revealed a complex regulatory network involving hormone signaling (ABA, JA, SA, GA, ET), stress responses, and light signaling. RT-qPCR expression profiling revealed that ten NtSTP genes (NtSTP1, 5, 7, 21, 22, 24, 26, 27, 28, and 29) exhibited significant transcriptional upregulation upon R. solanacearum infection. Specifically, NtSTP5, NtSTP7, NtSTP21, NtSTP22, NtSTP24, NtSTP26, and NtSTP27 peaked at 12 h post-inoculation (hpi), whereas NtSTP1, NtSTP28, and NtSTP29 reached their highest expression levels at 24 hpi. By contrast, NtSTP6, NtSTP13, and NtSTP30 displayed reduced expression upon R. solanacearum infection. These expression patterns indicate functional diversification within the NtSTP family and imply that these members may be transcriptionally modulated during plant responses to R. solanacearum. The present work provides preliminary and valuable candidate gene resources that may facilitate future disease resistance breeding programs in tobacco.

NtSTP gene family↗
PubMed1979

Specific labeling of a phosphate-transporting protein from rat-liver mitochondria by [203Hg]mersalyl.

1. A highly specific labeling of a phosphate-transporting protein from rat-liver mitochondria was obtained with [203Hg]mersalyl under the following conditions: (a) labeling of mitoplasts, isolated by the French-Press procedure; (b) washing of the isolated inner membranes with NaCl/octylglucoside. 2. The concentration-dependent labeling of the protein with mersalyl showed a biphasic saturation which correlated well with the protection and inhibition of phosphate transport. 3. The molecular weight (Mr 31000) and the amount of labeled carrier protein (24 nmol/g mitochondrial protein) at 100% protection correlated well with published data from the literature. 4. Gel filtration of the labeled protein in the presence of non-ionic detergents showed a molecular weight of at least twice of that obtained by gel electrophoresis in the presence of sodium dodecylsulfate.

Animals↗
PubMed1978

Horseradish peroxidase application to the protein transport investigations and alkaline phosphatase ultralocalization at the kidney barrier level.

Horseradish peroxidase was used to the precise investigation of low molecular protein transport across the kidney barrier. Simultaneously on the parallel material alkaline phosphatase activity was revealed, as this enzyme is connected with the transport processes through cell membranes. The applied reaction diaminebenzidine has shown infiltration spots for low molecular protein at the glomercular barrier and visualized tubular reabsorption of peroxidase in proximal convoluted tubule. Alkaline phosphatase activity has been observed on the surface of podocytes foot processes. On the surface of proximal convoluted tubules brush border and in canals formed with cells basal membranes investigations high activity of alkaline phosphatase was also observed.

Alkaline Phosphatase↗
PubMed1979

Structure of the anion-transport protein of the human erythrocyte membrane. Further studies on the fragments produced by proteolytic digestion.

The topology of the human erythrocyte membrane anion-transport protein (band 3) has been investigated by isolation and peptide 'mapping' of the major and minor fragments derived from proteolytic cleavage of the lactoperoxidase 125I-labelled protein in erythrocytes and erythrocyte membranes. The content, in each fragment, of lactoperoxidase 125I-labelled sites (which have a known location in the extracellular or cytoplasmic domain of the protein), together with the location of the sites of proteolytic cleavage yielding the fragments, has allowed us to determine the alignment of the fragments on the linear amino acid sequence and to infer the topology of the polypeptide in the membrane. The results suggest that a region in the C-terminal portion of the polypeptide forms part of the cytoplasmic domain of the protein in addition to a large N-terminal segment. The membrane-bound regions of the protein are located in the C-terminal two-thirds of the molecule. In this region the polypeptide chain traverses the membrane at least four times and an additional loop of polypeptide is either embedded in the membrane or also penetrates through it to the other surface. The location of the lectin receptors on the protein and the site of binding of an anion-transport inhibitor have also been studied.

Amino Acid Sequence↗
PubMed1977

Effects of alveolar hypoxia on lung fluid and protein transport in unanesthetized sheep.

To determine whether hypoxia directly affects pulmonary microvascular filtration of fluid or permeability to plasma proteins, we measured steady state lung lymph flow and protein transport in eight unanesthetized sheep breathing 10% O2 in N2 for 4 hours. We also studied three sheep breathing the same gas mixture for 48 hours. We surgically prepared the sheep to isolate and collect lung lymph and to measure average pulmonary arterial (Ppa) and left atrial (Pla) pressures. We placed a balloon catheter in the left atrium to elevate Pla. After recovery, the sheep breathed air through a tracheostomy for 2-4 hours, followed by 4 or 48 hours of hypoxia. In 13 4-hour studies, the average arterial PO2 fell from 97 to 38 torr; Ppa rose from 20 to 33 cm H2O; and lung lymph flow and lymph protein flow were unchanged. We also found that during 48-hour hypoxia, with a sustained elevation in Ppa and a decline in Pla, lymph flow and protein flow did not increase. In four sheep, we also raised Pla for 4 hours, followed by 4 hours of hypoxia with elevated Pla. Again, despite the added stress of elevated Pla, we found that lymph flow and lymph protein flow remained constant during hypoxia. We conclude that severe alveolar hypoxia, for 4 or 48 hours, alone or with increased pulmonary microvascular pressure, produced no change in lung fluid filtration or protein permeability, a finding supported by normal postmortem histology and extravascular lung water content.

Acute Disease↗
PubMed1978

Apparent half-lives of sugar transport proteins in Saccharomyces cerevisiae.

Using incubation in the presence of 0.4 mM cycloheximide the half-lives of the principal membrane transport proteins in baker's yeast were found to be: more than 24 h for the constitutive glucose carrier, 2.2 h for the inducible galactose carrier, 1.2 h for the inducible maltose carrier and 0.8 h for the inducible alpha-methyl-D-glucoside carrier. The distinct nature of the two last-named carriers was thus supported. De-induction of the galactose carrier was enhanced in the presence of glucose plus cycloheximide but not of either substance alone. Chloramphenicol suppressed all effects of cycloheximide. In contrast to the enzymes of galactose metabolism, the induction of the glactose carrier was not under the control of a mitochondrial factor and took place in a rho-mutant. The system induced by maltose but not the one induced by alpha-methyl-D-glucoside was de-induced rapidly by the intervention of a cytoplasm-synthesized protein.

Carbohydrate Metabolism↗
PubMed1977

The intra-axonal transport of polypeptide H: evidence for a fifth (very slow) group of transported proteins in the retinal ganglion cells of the rabbit.

We have determined that a genetically polymorphic polypeptide (H, molecular weight approximately equal to 195,000) of the rabbit nervous system is transported down the retinal ganglion cell axons at a velocity of 0.7-1.1 mm/day. The H-polypeptide and probably at least two additional polypeptides (molecular weights approximately 145,000 and 73,000) therefore compose a group of intra-axonally transported proteins which moves more slowly than the 4 groups previously described in these neurons. The polypeptides of this fifth group are similar in molecular weight to certain polypeptides transported slowly in other mammalian neurons.

Animals↗
PubMed1979

Taurine in the developing rabbit visual system: changes in concentration and axonal transport including a comparison with axonally transported proteins.

[35S]Taurine injected intravitreally into rabbits was transported axonally to the optic nerve terminals. Considerably more [35S]taurine was transported in young rabbits than in mature rabbits. The time course of taurine transport did not parallel that of proteins labeled with [3H]proline in the same system. The concentration of taurine in all components of the visual system, except retina, was greater in young animals than in mature animals, and was especially high in optic nerve. The possible functions of the high concentrations of taurine and the greater amount of axonally transported taurine in developing mammalian CNS are discussed.

Age Factors↗
PubMed1977

Characterization of proteins transported at different rates by axoplasmic flow in the dorsal root afferents of rats.

Proteins synthesized by soma located in L4 dorsal root ganglia and supplied to the axonal branches extending centrally in the dorsal root and peripherally towards the sciatic nerve were analyzed for radioactivity following injections of [3H] leucine into the L4 dorsal root ganglia. All proteins located in the dorsal root and sciatic nerve were analyzed by SDS acrylamide gel electrophoresis at various times post injection. The differences in radioactivity between the dorsal root and sciatic nerve proteins were mainly quantitative and not qualitative, with many proteins of various molecular weight ranges being transported into both segments. Generally, it appears that in both axonal branches the high molecular weight proteins are transported at the highest rate, medium weights slower and low molecular weight proteins slowest. More proteins of high and low molecular weights are transported into the dorsal root whereas more of those of medium molecular weight are transported towards the sciatic nerve.

Animals↗