Glucose transport capacity is not the rate-limiting step in the growth of some wild-type strains ofEscherichia coliandKlebsiella aerogenesin chemostat culture

Over a wide range of growth rates, two strains of Escherichia coli growing aerobically in continuous culture under glucose limitation utilized glucose at rates identical with those at which cells harvested from the chemostats transported [14C]glucose.

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A rare tRNA-Arg(CCU) that regulates Ty1 element ribosomal frameshifting is essential for Ty1 retrotransposition in Saccharomyces cerevisiae.

Genetics ◽

10.1093/genetics/135.2.309 ◽

1993 ◽

Vol 135 (2) ◽

pp. 309-320 ◽

Cited By ~ 7

Author(s):

K Kawakami ◽

S Pande ◽

B Faiola ◽

D P Moore ◽

J D Boeke ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Protein Processing ◽

Ribonuclease H ◽

Wild Type ◽

Ribosomal Frameshifting ◽

Translational Frameshifting ◽

Rate Limiting Step ◽

Limiting Step ◽

Ty1 Retrotransposition ◽

Rate Limiting

Abstract Translation of the yeast retrotransposon Ty1 TYA1(gag)-TYB1(pol) gene occurs by a +1 ribosomal frameshifting event at the sequence CUU AGG C. Because overexpression of a low abundance tRNA-Arg(CCU) encoded by the HSX1 gene resulted in a reduction in Ty1 frameshifting, it was suggested that a translational pause at the AGG-Arg codon is required for optimum frameshifting. The present work shows that the absence of tRNA-Arg(CCU) affects Ty1 transposition, translational frameshifting, and accumulation of mature TYB1 proteins. Transposition of genetically tagged Ty1 elements decreases at least 50-fold and translational frameshifting increases 3-17-fold in cells lacking tRNA-Arg(CCU). Accumulation of Ty1-integrase and Ty1-reverse transcriptase/ribonuclease H is defective in an hsx1 mutant. The defect in Ty1 transposition is complemented by the wild-type HSX1 gene or a mutant tRNA-Arg(UCU) gene containing a C for T substitution in the first position of the anticodon. Overexpression of TYA1 stimulates Ty1 transposition 50-fold above wild-type levels when the level of transposition is compared in isogenic hsx1 and HSX1 strains. Thus, the HSX1 gene determines the ratio of the TYA1 to TYA1-TYB1 precursors required for protein processing or stability, and keeps expression of TYB1 a rate-limiting step in the retrotransposition cycle.

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Coupled Glucose Transport and Metabolism in Cultured Neuronal Cells: Determination of the Rate-Limiting Step

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1995.102 ◽

1995 ◽

Vol 15 (5) ◽

pp. 814-826 ◽

Cited By ~ 22

Author(s):

Richard R. Whitesell ◽

Michael Ward ◽

Anthony L. McCall ◽

Daryl K. Granner ◽

James M. May

Keyword(s):

Glucose Transport ◽

Glucose Utilization ◽

Neuroblastoma Cell ◽

Neuronal Cells ◽

Neuronal Cell ◽

Cell Types ◽

Rate Limiting Step ◽

Limiting Step ◽

Rate Limiting ◽

Intracellular Glucose

In brain and nerves the phosphorylation of glucose, rather than its transport, is generally considered the major rate-limiting step in metabolism. Since little is known regarding the kinetic coupling between these processes in neuronal tissues, we investigated the transport and phosphorylation of [2-3H]glucose in two neuronal cell models: a stable neuroblastoma cell line (NCB20), and a primary culture of isolated rat dorsal root ganglia cells. When transport and phosphorylation were measured in series, phosphorylation was the limiting step, because intracellular glucose concentrations were the same as those outside of cells, and because the apparent Km for glucose utilization was lower than expected for the transport step. However, the apparent Km was still severalfold higher than the Km of hexokinase I. When [2-3H]glucose efflux and phosphorylation were measured from the same intracellular glucose pool in a parallel assay, rates of glucose efflux were three- to-fivefold greater than rates of phosphorylation. With the parallel assay, we observed that activation of glucose utilization by the sodium channel blocker veratridine caused a selective increase in glucose phosphorylation and was without effect on glucose transport. In contrast to results with glucose, both cell types accumulated 2-deoxy-d-[14C]glucose to concentrations severalfold greater than extracellular concentrations. We conclude from these studies that glucose utilization in neuronal cells is phosphorylation-limited, and that the coupling between transport and phosphorylation depends on the type of hexose used.

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Rate-limiting steps for insulin-mediated glucose uptake into perfused rat hindlimb

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1986.250.1.e100 ◽

1986 ◽

Vol 250 (1) ◽

pp. E100-E102 ◽

Cited By ~ 13

Author(s):

K. Kubo ◽

J. E. Foley

Keyword(s):

Glucose Uptake ◽

Glucose Transport ◽

Transport System ◽

Glucose Concentration ◽

Rate Limiting Step ◽

Limiting Step ◽

Glucose Transport System ◽

Glucose Clearance ◽

Rate Limiting ◽

Uptake And Metabolism

To determine the glucose and insulin concentrations at which glucose transport is rate limiting for insulin-mediated glucose uptake and metabolism in muscle, glucose clearance was determined in the presence of glucose concentrations ranging from trace to 20 mM and in the absence or presence of insulin in the perfused rat hindlimb. In the absence of insulin and at submaximally stimulating insulin concentrations glucose clearance was constant up to 7 mM glucose and then decreased as the glucose concentration was raised. At maximally stimulating insulin concentrations glucose clearance was constant up to 2 mM glucose and then decreased. The decrease in glucose clearance between 2 and 7 mM glucose in the presence of maximally stimulating insulin concentrations could not be accounted for by competition among glucose molecules for the glucose transport system. The results suggest that at physiological glucose concentrations in the presence of maximally stimulating insulin concentrations the rate-limiting step for insulin-mediated glucose uptake and metabolism in muscle shifts from glucose transport to some step beyond transport.

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The rate-limiting step for glucose transport into the hypothalamus is across the blood-hypothalamus interface

Journal of Neurochemistry ◽

10.1111/j.1471-4159.2009.05934.x ◽

2009 ◽

Vol 109 ◽

pp. 38-45 ◽

Cited By ~ 14

Author(s):

Carol Poitry-Yamate ◽

HongXia Lei ◽

Rolf Gruetter

Keyword(s):

Glucose Transport ◽

Rate Limiting Step ◽

Limiting Step ◽

Rate Limiting

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THE UPTAKE OF GLUCOSE INTO CELLS AND THE ROLE OF INSULIN IN GLUCOSE TRANSPORT

Canadian Journal of Biochemistry ◽

10.1139/o64-105 ◽

1964 ◽

Vol 42 (6) ◽

pp. 933-944 ◽

Cited By ~ 10

Author(s):

Margaret J. Henderson

Keyword(s):

Cell Membrane ◽

Glucose Uptake ◽

Glucose Transport ◽

Glucose Levels ◽

Insulin Transport ◽

Rate Limiting Step ◽

Limiting Step ◽

Extracellular Glucose ◽

Rate Limiting

This presentation has been restricted to the role of insulin in glucose transport in muscle cells and deals mainly with experiments using the perfused rat heart. The several possible means for glucose transfer into cells, diffusion, pores, pinocytosis, carriers, and dimerization, have been discussed; and arguments in favor of the carrier theory, namely, specificity, kinetics, inhibition, competition, and counterflow, have been elaborated. Glucose uptake has been considered to consist of three sequential steps: (1) passage of glucose from within the capillary to the cell surface, (2) transport across the cell membrane, and (3) metabolism of glucose within the cell. The first is considered to take place by diffusion and not to be significantly limiting under normal conditions, nor to be influenced by insulin. Transport across the cell membrane is thought to be mainly under the control of insulin and is the major rate-limiting step in glucose uptake when the extracellular glucose levels are in the normal range. Metabolism of glucose within the cell is the major rate-limiting step in glucose uptake when intracellular glucose concentration is so high that its phosphorylation is near saturation.

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The rate-limiting step in yeast PGK1 mRNA degradation is an endonucleolytic cleavage in the 3'-terminal part of the coding region.

Molecular and Cellular Biology ◽

10.1128/mcb.12.7.2986 ◽

1992 ◽

Vol 12 (7) ◽

pp. 2986-2996 ◽

Cited By ~ 52

Author(s):

P Vreken ◽

H A Raué

Keyword(s):

Half Life ◽

Rnase H ◽

Start Codon ◽

Wild Type ◽

Coding Region ◽

Endonucleolytic Cleavage ◽

Rate Limiting Step ◽

Limiting Step ◽

Nuclease Mapping ◽

Rate Limiting

Insertion of an 18-nucleotide-long poly(G) tract into the 3'-terminal untranslated region of yeast phosphoglycerate kinase (PGK1) mRNA increases its chemical half-life by about a factor of 2 (P. Vreken, R. Van der Veen, V. C. H. F. de Regt, A. L. de Maat, R. J. Planta, and H. A. Raué, Biochimie 73:729-737, 1991). In this report, we show that this insertion also causes the accumulation of a degradation intermediate extending from the poly(G) sequence down to the transcription termination site. Reverse transcription and S1 nuclease mapping experiments demonstrated that this intermediate is the product of shorter-lived primary fragments resulting from endonucleolytic cleavage immediately downstream from the U residue of either of two 5'-GGUG-3' sequences present between positions 1100 and 1200 close to the 3' terminus (position 1251) of the coding sequence. Similar endonucleolytic cleavages appear to initiate degradation of wild-type PGK1 mRNA. Insertion of a poly(G) tract just upstream from the AUG start codon resulted in the accumulation of a 5'-terminal degradation intermediate extending from the insertion to the 1100-1200 region. RNase H degradation in the presence of oligo(dT) demonstrated that the wild-type and mutant PGK1 mRNAs are deadenylated prior to endonucleolytic cleavage and that the half-life of the poly(A) tail is three- to sixfold lower than that of the remainder of the mRNA. Thus, the endonucleolytic cleavage constitutes the rate-limiting step in degradation of both wild-type and mutant PGK1 transcripts, and the resulting fragments are degraded by a 5'----3' exonuclease, which appears to be severely retarded by a poly(G) sequence.

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DNA replication licensing in stem cells: Gatekeeping the commitment to proliferation

The Journal of Cell Biology ◽

10.1083/jcb.201803037 ◽

2018 ◽

Vol 217 (5) ◽

pp. 1563-1565

Author(s):

Hilary A. Coller

Keyword(s):

Stem Cells ◽

Dna Replication ◽

Intestinal Stem Cells ◽

Wild Type ◽

Rate Limiting Step ◽

Limiting Step ◽

Cell Biol ◽

Rate Limiting

Carroll et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201708023) developed a method to assess DNA replication licensing in tissues. They show that intestinal stem cells within wild-type crypts, but not in crypts with cancer-causing mutations, are largely unlicensed, suggesting that licensing may represent a rate-limiting step in the commitment to proliferation.

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Is the 135S Poliovirus Particle an Intermediate during Cell Entry?

Journal of Virology ◽

10.1128/jvi.74.18.8757-8761.2000 ◽

2000 ◽

Vol 74 (18) ◽

pp. 8757-8761 ◽

Cited By ~ 43

Author(s):

Yan Huang ◽

James M. Hogle ◽

Marie Chow

Keyword(s):

Conformational Transition ◽

Cell Entry ◽

Wild Type ◽

Cold Adapted ◽

Rate Limiting Step ◽

Limiting Step ◽

A Cell ◽

Low Efficiency ◽

Rate Limiting ◽

Initial Conversion

ABSTRACT Poliovirus binding to its receptor (PVR) on the cell surface induces a conformational transition which generates an altered particle with a sedimentation value of 135S versus the 160S of the native virion. A number of lines of evidence suggest that the 135S particle is a cell entry intermediate. However, the low infection efficiencies of the 135S particle and the absence of detectable 135S particles during infection at 26°C by the cold-adapted mutants argue against a role for the 135S particle during the cell entry process. We show here that binding of 135S-antibody complexes to the Fc receptor (CDw32) increases the infectivity of these particles by 2 to 3 orders of magnitude. Thus, the low efficiency of infection by 135S particles is due in part to the low binding affinity of these particles. In addition, we show that there is an additional stage in the entry process that is associated with RNA release. This stage occurs after formation of the 135S particle, is rate limiting during infection at 37°C, but not at 26°C, and is PVR independent. The data also demonstrate that during infection at 26°C, the rate-limiting step is the PVR-mediated conversion of wild-type 160S particles to 135S particles. This suggests that during infection at 26°C by the cold-adapted viruses, 135S particles are formed, but they fail to accumulate to detectable levels because the subsequent post-135S particle events occur at a significantly faster rate than the initial conversion of 160S to 135S particles. These data support a model in which the 135S particle is an intermediate during poliovirus entry.

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